DCCCD Biology the Major Stages of The Cell Cycle Questions

Because learning changes everything.® Chapter 20 Viruses, Bacteria, and Archaea BIOLOGY Fourteenth Edition Sylvia S. Mader Michael Windelspecht Chapter Opener 20 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 2 Table 20.1 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 3 UnFigure 20.1 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 4 Figure 20.1 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 5 Figure 20A1 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 6 Figure 20A2 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 7 Figure 20.2 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 8 Figure 20.3 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 9 Figure 20B Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 10 Figure 20C Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 11 Figure 20.4 Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. 12 UnFigure 20.2 Copyright 2022 © McGraw Hill LLC. All rights reserved. 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No reproduction or distribution without the prior written consent of McGraw Hill LLC. 25 Because learning changes everything.® Biology Sylvia S. Mader Michael Windelspecht Chapter 9 The Cell Cycle and Cellular Reproduction Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Outline 9.1 The Cell Cycle 9.2 The Eukaryotic Chromosome 9.3 Mitosis and Cytokinesis 9.4 The Cell Cycle and Cancer 9.5 Prokaryotic Cell Division © McGraw Hill LLC 2 9.1 The Cell Cycle The cell cycle is an orderly set of stages from the first division of a eukaryotic cell to the time the resulting daughter cells divide. Just prior to the next division: • Cell grows larger. • Number of organelles doubles. • DNA is replicated. The two major stages of the cell cycle: • Interphase (includes several stages). • Mitotic stage (includes mitosis and cytokinesis). © McGraw Hill LLC 3 The Cell Cycle Process Figure 9.1 Access the text alternative for slide images. © McGraw Hill LLC 4 Interphase Overview © McGraw Hill LLC 5 Stages of Interphase © McGraw Hill LLC 6 Sister Chromatids Figure 9.2 © McGraw Hill LLC 7 M (Mitotic) Stage Includes: ■ Mitosis. • Nuclear division. • Daughter chromosomes are distributed by the mitotic spindle to two daughter nuclei. ■ Cytokinesis. • Division of the cytoplasm. Results in two genetically identical daughter cells. © McGraw Hill LLC 8 Control of the Cell Cycle © McGraw Hill LLC 9 Apoptosis Apoptosis is programmed cell death. It involves a sequence of cellular events that bring about the destruction of the cell. • Fragmenting of the nucleus. • Blistering of the plasma membrane. • Engulfing of cell fragments by white blood cells or other cells. Apoptosis is caused by enzymes called caspases. Cell division and apoptosis are opposing forces. • Cell division increases cell numbers. • Apoptosis decreases cell numbers. © McGraw Hill LLC 10 Apoptosis Events Figure 9.3 Access the text alternative for slide images. © McGraw Hill LLC (photo): Steve Gschmeissner/Science Source 11 Apoptosis and Cell Division © McGraw Hill LLC 12 Regulation at the G1 Checkpoint Figure 9A Figure 9B © McGraw Hill LLC Access the text alternative for slide images. 13 9.2 The Eukaryotic Chromosome Contains a single DNA molecule (double helix). DNA is associated with histones (proteins). DNA and histone proteins are collectively called chromatin. ■ Histones. • • • • Play a structural role. Have essential survival functions. Primarily 5 types. Responsible for DNA packing into nucleus. DNA wound around the core of 8 histone molecules is called a nucleosome, which appears as a string of beads. ■ Nucleosomes joined together by “linker” DNA appear as beads on a string. ■ The string “folds” into a compact zigzag structure. ■ Then it loops into radial loops. ■ It is loosely coiled. ■ Euchromatin represents the active chromatin that can be transcribed by RNA polymerase and transcription factors. © McGraw Hill LLC 14 Structure of the Eukaryotic Chromosome Figure 9.4 Access the text alternative for slide images. (photos) (a): Gopal Murti/DIOMEDIA; (b): Courtesy Dr. Jerome Rattner, Cell Biology and Anatomy, University of Calgary; (c): Courtesy of Ulrich Laemmli and J.R. Paulson, Dept. of Molecular Biology, University of Geneva, Switzerland; (d, e): ©Peter Engelhardt, Haartman Institute/University of Helsinki/and NMC/Department of Applied Physics/Aalto © McGraw Hill LLC University/School of Science and Technology/Helsinki, Finland 15 Heterochromatin A more highly compacted form of the chromosome is heterochromatin. ■ Inactive chromatin. ■ Genes hardly ever transcribed. ■ Compact chromosomes are more easily moved than extended chromatin. ■ Most chromosomes have both compaction levels. © McGraw Hill LLC 16 9.3 Mitosis and Cytokinesis Eukaryotic cell division involves mitosis (nuclear division) and cytokinesis (division of cytoplasm). During mitosis, sister chromatids are separated and distributed to daughter cells. Before mitosis begins: • Chromatin condenses (coils) into distinctly visible chromosomes. • Each species has a characteristic chromosome number. © McGraw Hill LLC 17 Diploid Chromosome Numbers of Some Eukaryotes Table 9.1 Diploid Chromosome Numbers of Some Eukaryotes Type of Organism Name of Chromosome Fungi Saccharomyces cerevisiae (yeast) 32 Plants Pisum sativum (garden pea) 14 Solanum tuberosum (potato) 48 Ophioglossum vulgatum (southern adder’s tongue fern) 1,320 Animals © McGraw Hill LLC Chromosome Number Drosophila melanogaster (fruit fly) 8 Homo sapiens (human) 46 Carassius auratus (goldfish) 94 18 Chromosome Number © McGraw Hill LLC 19 Chromosome Duplication During interphase, a cell prepares for cell division. Organelles are duplicated including centrosome. At the end of S stage: Each chromosome internally duplicated. Consists of two identical double-helical DNA molecules. ■ Sister chromatids (two strands of genetically identical chromosomes). ■ Attached together at a single point (called centromere). During mitosis: Centromeres holding sister chromatids together separate. Sister chromatids separate. Each becomes a daughter chromosome. Daughter chromosomes of each type are distributed to the opposite daughter nuclei. © McGraw Hill LLC 20 Duplicated Chromosomes Figure 9.5 Access the text alternative for slide images. © McGraw Hill LLC (a): Andrew Syred/Science Source 21 Division of the Centrosome Just outside the nucleus is the centrosome. This is the microtubule-organizing center in animal cells. The centrosome was also replicated in S stage of interphase, so there are two centrosomes before mitosis begins. ■ In animals, the centrosome contains two barrel-shaped centrioles. • Oriented at right angles to each other within the centrosome. Centrosome organizes the mitotic spindle. ■ The spindle contains many fibers. ■ Each fiber is composed of a cylindrical bundle of microtubules. ■ Microtubules assemble when tubulin subunits join, and when the subunits disassemble, they form mitotic spindle fibers or allow the cell to change shape for cell division. © McGraw Hill LLC 22 Prophase Nuclear division is about to occur. ■ Chromatin condensed. • Chromosomes are distinguishable with microscope. • Each chromosome has two sister chromatids held together at the centromere. ■ Nucleolus disappears. ■ Nuclear envelope fragments. ■ Spindle begins to assemble. ■ Two centrosomes move away from each other. ■ In animal cells, microtubules form star-like arrays termed asters. © McGraw Hill LLC 23 Prometaphase Preparations for sister chromatid separation are evident. The centromere of each chromosome develops two kinetochores. • Specialized protein complex. • One attached to each sister chromatid. • Physically connect sister chromatids with specialized microtubules (kinetochores). • These connect sister chromatids to opposite poles of the mother cell. © McGraw Hill LLC 24 Metaphase and Anaphase Metaphase ■ Chromosomes pulled around by kinetochore fibers. ■ Forced to align across the equatorial plane of the cell. • Metaphase plate – Represents plane through which mother cell will be divided. • Nonattached, polar spindle fibers overlap. • M checkpoint delays the start of anaphase until kinetochores are attached properly. Anaphase ■ Centromere dissolves, releasing sister chromatids. ■ Sister chromatids separate at the centromere. • Now called daughter chromosomes. • Pulled to opposite poles along kinetochore fibers. • The poles move farther apart. © McGraw Hill LLC 25 Telophase The spindle disappears. New nuclear envelopes form around daughter chromosomes. There are now two clusters of daughter chromosomes. • Still, there are two of each type with all types represented. • Clusters are daughter nuclei. • Nuclear envelopes form around the two daughter nuclei. • Each daughter nucleus receives one chromosome of each type. Division of the cytoplasm requires cytokinesis. Chromosomes become diffused chromatin once again. © McGraw Hill LLC 26 Phases of Mitosis in Animal and Plant Cells 1 Figure 9.6 Access the text alternative for slide images. (photos): (animal early prophase, animal prophase, animal metaphase, animal anaphase, animal telophase, plant early prophase, plant prometaphase): ©Ed Reschke; (animal prometaphase): Michael Abbey/Science Source; (plant prophase, plant metaphase, plant anaphase, plant telophase): Kent Wood/Science Source © McGraw Hill LLC 27 Phases of Mitosis in Animal and Plant Cells 2 Figure 9.6 animal cell (early prophase); plant cell (early prophase): ©Ed Reschke © McGraw Hill LLC 28 Phases of Mitosis in Animal and Plant Cells 3 Figure 9.6 © McGraw Hill LLC animal cell (early prophase, prophase): ©Ed Reschke; plant cell (early prophase): ©Ed Reschke; plant cell (prophase): Kent Wood/Science Source 29 Phases of Mitosis in Animal and Plant Cells 4 Figure 9.6 Access the text alternative for slide images. animal cell (early prophase, prophase): ©Ed Reschke; animal cell (prometaphase): Michael Abbey/Science Source; plant cell (early prophase, prometaphase): ©Ed Reschke; plant cell (prophase): Kent Wood/Science Source © McGraw Hill LLC 30 Phases of Mitosis in Animal and Plant Cells 5 Figure 9.6 Access the text alternative for slide images. animal cell (early prophase, prophase, metaphase): ©Ed Reschke; animal cell (prometaphase): Michael Abbey/Science Source; plant cell (early prophase, prometaphase): ©Ed Reschke; plant cell (prophase, metaphase): Kent Wood/Science Source © McGraw Hill LLC 31 Phases of Mitosis in Animal and Plant Cells 6 Figure 9.6 Access the text alternative for slide images. animal cell (early prophase, prophase, metaphase, anaphase): ©Ed Reschke; animal cell (prometaphase): Michael Abbey/Science Source; plant cell (early prophase, prometaphase): ©Ed Reschke; plant cell (prophase, metaphase, anaphase): Kent Wood/Science Source © McGraw Hill LLC 32 Phases of Mitosis in Animal and Plant Cells 7 Figure 9.6 © McGraw Hill LLC animal cell (early prophase, prophase, metaphase, anaphase, telophase): ©Ed Reschke; animal cell (prometaphase): Michael Abbey/Science Source; plant cell (early prophase, prometaphase): ©Ed Reschke; plant cell (prophase, metaphase, anaphase, telophase): Kent Wood/Science Source 33 Cytokinesis in Plant and Animal Cells Cytokinesis = division of cytoplasm. Allocates the mother cell’s cytoplasm equally to daughter nucleus. Encloses each daughter cell in its own plasma membrane. Often begins in anaphase. Proceeds differently in plant and animal cells. Animal cytokinesis: • Cleavage furrow appears between daughter nuclei. • Formed by a contractile ring of actin filaments. • Like pulling on a drawstring. • Eventually pinches the mother cell in two. © McGraw Hill LLC 34 Cytokinesis in Plant Cells 1 Cytokinesis in plant cells begins with the formation of a cell plate. • Rigid cell walls outside plasma membrane do not permit furrowing. • Many small membrane-bounded vesicles are made by Golgi apparatus. • They eventually fuse into one thin vesicle extending across the mother cell. • The membranes of the cell plate become the plasma membrane between the daughter cells. • The space between the daughter cells becomes filled with the middle lamella. • Daughter cells later secrete primary cell walls on opposite sides of the middle lamella, which cements the primary cell walls together. © McGraw Hill LLC 35 Cytokinesis in Animal Cells Figure 9.7 © McGraw Hill LLC (photos): (top): National Institutes of Health(NIH)/USHHS; (bottom): Steve Gschmeissner/SPL/Getty RF 36 Cytokinesis in Plant Cells 2 Figure 9.8 © McGraw Hill LLC (photo): ©Biophoto Associates/Science Source 37 The Functions of Mitosis It permits growth and repair. In flowering plants, meristematic tissue retains the ability to divide throughout the life of the plant. Trees increase their girth (width) each growing season. In mammals, mitosis is necessary when: ■ A fertilized egg becomes an embryo. ■ An embryo becomes a fetus. ■ After birth, a child becomes an adult. ■ A cut heals or a broken bone mends. © McGraw Hill LLC 38 Stem Cells Many mammalian organs contain stem cells. ■ They retain the ability to divide. ■ Red bone marrow stem cells divide to produce various types of blood cells. Therapeutic cloning to produce human tissues can begin with either adult stem cells or embryonic stem cells. Embryonic stem cells can be used for reproductive cloning, the production of a new individual. © McGraw Hill LLC 39 Two Types of Cloning Figure 9C Access the text alternative for slide images. © McGraw Hill LLC 40 9.4 The Cell Cycle and Cancer Abnormal growth of cells is called a tumor. Benign tumors are not cancerous. ■ Encapsulated. ■ Do not invade neighboring tissue or spread. Malignant tumors are cancerous. ■ Not encapsulated. ■ Readily invade neighboring tissues. ■ May also detach and lodge in distant places (metastasis). ■ Results from mutation of genes regulating the cell cycle. Development of cancer • Tends to be gradual and multistep. • May take years before cell is obviously cancerous. © McGraw Hill LLC 41 Characteristics of Cancer Cells 1 Lack differentiation ■ Cells are non-specialized. ■ Cells are immortal (can enter cell cycle repeatedly). Have abnormal nuclei ■ Cells may be enlarged. ■ Cells may have abnormal number of chromosomes. ■ Cells often have extra copies of genes. Do not undergo apoptosis ■ Normally, cells with damaged DNA undergo apoptosis. ■ The immune system can also recognize abnormal cells and trigger apoptosis. ■ Cancer cells are abnormal but fail to undergo apoptosis. © McGraw Hill LLC 42 Characteristics of Cancer Cells 2 Form tumors ■ Mitosis is normally controlled by contact with neighboring cells: contact inhibition. • Cancer cells have lost contact inhibition. Undergo metastasis ■ The original tumor easily fragments. ■ New tumors appear in other organs. Undergo angiogenesis ■ They form new blood vessels. • They bring nutrients and oxygen to the tumor. © McGraw Hill LLC 43 Progression of Cancer Figure 9.9 © McGraw Hill LLC Access the text alternative for slide images. 44 Cancer Cells Versus Normal Cells Table 9.2 Cancer Cells Versus Normal Cells Cancer Cells Normal Cells Nondifferentiated cells Differentiated cells Abnormal nuclei Normal nuclei Do not undergo apoptosis Undergo apoptosis No contact inhibition Contact inhibition Disorganized, multilayered One organized layer Undergo metastasis Remain in original tissue © McGraw Hill LLC 45 Origin of Cancer Normal growth and tissue maintenance depends on a balance between signals that promote and inhibit cell division. Two types of genes may be mutated when the balance is upset, which may cause cancer. Oncogenes ■ Proto-oncogenes code for proteins which promote the cell cycle in various ways. ■ If a proto-oncogene is mutated, it may become an oncogene. Tumor suppressor genes code for proteins which inhibit the cell cycle and promote apoptosis in various ways. ■ If a tumor suppressor gene becomes inactive, it may promote cancer development. Both proto-oncogenes and tumor suppressor genes are normally regulated in coordination with organism’s growth plan. © McGraw Hill LLC 46 Causes of Cancer Figure 9.10 © McGraw Hill LLC Access the text alternative for slide images. 47 Proto-oncogenes Become Oncogenes Proto-oncogenes are normal genes which are part of a stimulatory pathway. They promote progression through the cell cycle. They include receptors and signaling molecules. Mutations in proto-oncogenes cause them to become oncogenes. ■ These can specify an abnormal protein product or produce abnormally high levels of a normal product. ■ Uncontrolled cell division results. ■ There are 100 oncogenes which can lead to tumors. • Example is BRCA1, mutations of which can cause breast and ovarian cancer. © McGraw Hill LLC 48 Tumor Suppressor Genes Become Inactive These directly inhibit the cell cycle and prevent cells from dividing uncontrollably. Some tumor suppressors promote apoptosis. A mutation in a tumor suppressor causes the cell cycle to accelerate. ■ Examples are the RB and p53 genes which code for proteins with the same names. • Retinoblastoma is an inherited condition that results from a mutation in the RB gene. • The p53 gene turns on the expression of other cell cycle inhibitory genes. • Half of human cancers involve an abnormal or deleted p53 gene. © McGraw Hill LLC 49 Other Causes of Cancer Chromosomes normally have special material at each end called telomeres. These get shorter each cell division. When they get very short, the cell will no longer divide. Telomerase is an enzyme that maintains the length of telomeres. Mutations in telomerase gene: • Cause telomeres to continue to lengthen, which. • Allows cancer cells to continually divide. © McGraw Hill LLC 50 9.5 Prokaryotic Cell Division The prokaryotic (bacteria and archaea) chromosome is a ring of DNA and a few associated proteins. • Folded up in an area called the nucleoid. • 1,000× the length of cell. • Replicated into two rings prior to cell division. • Replicated rings attach to the plasma membrane. Binary fission • Splitting in two. • Two replicate chromosomes are distributed to two daughter cells. • Produces two daughter cells identical to original cell—asexual reproduction. • Escherichia coli, an intestinal microbe, has a generation time of about 20 minutes. © McGraw Hill LLC 51 Comparing Prokaryotes and Eukaryotes Binary fission and mitosis both ensure that the daughter cell is genetically identical to the parent. Prokaryotes, protists (many algae and protozoans), and some fungi (yeasts) are single-celled. • Cell division of single-celled organisms produces two new individuals. In multicellular fungi, plants, and animals, cell division is important for growth, renewal, and repair. During binary fission, the chromosome duplicates and each daughter receives one copy as the parent cell elongates and a new cell wall and membrane form between daughter cells. No spindle is involved in binary fission. © McGraw Hill LLC 52 Binary Fission 1 Figure 9.13 Access the text alternative for slide images. © McGraw Hill LLC ©Scimat/Science Source 53 Binary Fission 2 Figure 9.13 © McGraw Hill LLC ©Scimat/Science Source 54 Binary Fission 3 Figure 9.13 © McGraw Hill LLC ©Scimat/Science Source 55 Binary Fission 4 Figure 9.13 © McGraw Hill LLC ©Scimat/Science Source 56 Binary Fission 5 Figure 9.13 Access the text alternative for slide images. © McGraw Hill LLC ©Scimat/Science Source 57 Functions of Cell Division Table 9.3 Functions of Cell Division Type of Organism Cell Division Function Binary fission Asexual reproduction Protists and some fungi (yeast) Mitosis and cytokinesis Asexual reproduction Other fungi, plants, and animals Mitosis and cytokinesis Development, growth, and repair Prokaryotes Bacteria and archaea Eukaryotes © McGraw Hill LLC 58 Because learning changes everything.® www.mheducation.com Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Accessibility Content: Text Alternatives for Images © McGraw Hill LLC 60 The Cell Cycle Process – Text Alternative Return to parent-slide containing images. Interphase includes G1, S, and G2 phase. G1: growth. G1 checkpoint: cell cycle main checkpoint. If DNA is damaged, apoptosis will occur. Otherwise, the cell is committed to divide when growth signals are present and nutrients are available. S: growth and DNA replication. G2: growth and final preparations for division. G2 checkpoint: Mitosis checkpoint. Mitosis will occur if DNA has replicated properly. Apoptosis will occur if the DNA is damaged and cannot be repaired. M phase includes mitosis, which includes prophase, prometaphase, metaphase, anaphase and telophase, along with cytokinesis. M checkpoint: spindle assembly checkpoint. Mitosis will not continue if chromosomes are not properly aligned. Return to parent-slide containing images. 61 © McGraw Hill LLC Apoptosis Events – Text Alternative Return to parent-slide containing images. Left panel: Normal cells lead to rounding of cell with collapsing of nucleus , which leads to condensing of chromatin and fragmentation of nucleus, leading to plasma membrane blisters, and formation of blebs (curves across the circumference of cell), which finally leads to fragmenting of cell containing DNA fragments. Right panel: A micrograph (enlarged 2500 times) shows cluster of ovular cell fragments in an apoptotic cell. Return to parent-slide containing images. 62 © McGraw Hill LLC Regulation at the G1 Checkpoint – Text Alternative Return to parent-slide containing images. (Top Image) E2 factor not released (reversible): E2 factor is attached to retinoblastoma protein (where cyclin-dependent-kinase is not present) Phosphorylated retinoblastoma: E2 factor is attached to retinoblastoma protein (where cyclin-dependent-kinase is present with two phosphate groups) Released E2 factor: E2 factor is released. E2 factor binds to DNA: DNA passes through cell cycle proteins. (Bottom Image) Tumor protein (with no DNA damage) results in breakdown of protein. Tumor protein (with DNA damage) with a phosphate group results in phosphorylated tumor protein, which leads to DNA passing through phosphorylated tumor protein during DNA repair proteins, where tumor protein binds to DNA and carries out process of apoptosis. Return to parent-slide containing images. 63 © McGraw Hill LLC Structure of the Eukaryotic Chromosome – Text Alternative Return to parent-slide containing images. A. B. C. D. E. Nucleosomes (visible as beads on a string): DNA double helix: 2 nanometers Nucleosome: 11 nanometers Wrapping of DNA around histone proteins forms nucleosomes. 30 nanometer fiber: Histone H1: 30 nanometer. Formation of a three-dimensional zigzag structure via histone H1 and other DNA-binding proteins. Radial loop domains: Euchromatin: 300 nanometers. Loose coiling into radial loops. Heterochromatin: 700 nanometers. Tight compaction of radial loops to form heterochromatin. Metaphase chromosome: 1400 nanometers. Metaphase chromosome forms with the help of a protein scaffold. Return to parent-slide containing images. 64 © McGraw Hill LLC Duplicated Chromosomes – Text Alternative Return to parent-slide containing images. A. B. Micrograph shows fuzzy textured duplicated chromosomes. Diagram of duplicated chromosomes shows a two sister chromatids, with a centromere attaching the two and an ovular kinetochore at two ends of centromere. Return to parent-slide containing images. 65 © McGraw Hill LLC Phases of Mitosis in Animal and Plant Cells – Text Alternative 1 Return to parent-slide containing images. Micrographs and illustrations show positioning of centrosomes, spindle fibers, inherited and newly duplicated chromosomes during distinct phases of mitosis. After daughter cells form, chromosomes become indistinct chromatin. Return to parent-slide containing images. 66 © McGraw Hill LLC Phases of Mitosis in Animal and Plant Cells – Text Alternative 4 Return to parent-slide containing images. In prometaphase, kinetochore of each chromatid is attached to a kinetochore spindle fiber. Polar spindle fibers stretch from each spindle pole and overlap. Return to parent-slide containing images. 67 © McGraw Hill LLC Phases of Mitosis in Animal and Plant Cells – Text Alternative 5 Return to parent-slide containing images. In metaphase, centromeres of duplicated chromosomes are aligned at the metaphase plate (center of fully formed spindle). Kinetochore spindle fibers attached to the sister chromatids come from opposite spindle poles. Return to parent-slide containing images. 68 © McGraw Hill LLC Phases of Mitosis in Animal and Plant Cells – Text Alternative 6 Return to parent-slide containing images. In anaphase, sister chromatids part and become daughter chromosomes that move toward the spindle poles. In this way, each pole receives the same number and kinds of chromosomes as the parent cell. Return to parent-slide containing images. 69 © McGraw Hill LLC Two Types of Cloning – Text Alternative Return to parent-slide containing images. A. Reproductive cloning: G sub 0 cells are received from animal to be cloned, where G sub 0 nucleus is removed. Another egg, whose nucleus is removed and discarded is fused with G sub 0 nucleus and cultured to form embryonic stem cells, where the embryo is implanted into surrogate mother resulting in a clone. B. Therapeutic cloning: G sub 0 somatic cells, where G sub 0 nucleus is removed. Another egg, whose nucleus is removed and discarded is fused with G sub 0 nucleus and cultured to form embryonic stem cells resulting in formation of three sets of specific nervous, blood and muscle cells. Return to parent-slide containing images. 70 © McGraw Hill LLC Progression of Cancer – Text Alternative Return to parent-slide containing images. The progression is as follows: New mutations arise, and one cell (brown) has the ability to start a tumor. Cancer in situ. The tumor is at its place of origin. One cell (purple) mutates further. Cancer cells now have the ability to invade the circular lymphatic and blood vessels and travel throughout the body. New metastatic tumors are found some distance from the primary tumor. Return to parent-slide containing images. 71 © McGraw Hill LLC Causes of Cancer – Text Alternative Return to parent-slide containing images. A. B. C. Influences that cause mutated proto-oncogenes (called oncogenes) and mutated tumor suppressor genes: Heredity, radiation sources, pesticides and herbicides and viruses. Effect of growth factor: Diagram of plasma membrane with layers of phospholipids, where a U-shaped receptor protein holds a spherical growth factor. The phosphate group adheres to triangular inactive signaling protein resulting in formation of activated signaling protein, inside the cell. Stimulatory pathway and inhibitory pathway: A lateral cutaway diagram of cell shows stimulatory pathway (where gene product promotes cell cycle) and inhibitory pathway (where gene product inhibits cell cycle) with following data: Growth factor: Activates signaling proteins in a stimulatory pathway that extends to the nucleus. Proto-oncogene: Codes for a growth factor, a receptor protein, or a signaling protein in a stimulatory pathway. If a proto-oncogene becomes an oncogene, the end result can be active cell division. Tumor suppressor gene: Codes for a signaling protein in an inhibitory pathway. If a tumor suppressor gene mutates, the end result can be activeReturn cell division. to parent-slide containing images. 72 © McGraw Hill LLC Binary Fission – Text Alternative 1 Return to parent-slide containing images. Cross-sectional diagram of cell on the right shows labels for chromosome, cell wall, plasma membrane, and cytoplasm. Return to parent-slide containing images. 73 © McGraw Hill LLC Binary Fission – Text Alternative 5 Return to parent-slide containing images. Stages of cell fission include 1. Attachment of chromosome to a special plasma membrane site indicates that this bacterium is about to divide. 2. The cell is preparing for binary fission by enlarging its cell wall, plasma membrane, and overall volume. 3. DNA replication has produced two identical chromosomes. Cell wall and plasma membrane begin to grown inward. 4. As the cell elongates, the chromosomes are pulled apart. Cytoplasm is being distributed evenly. 5. New cell wall and plasma membrane have divided the daughter cells. Return to parent-slide containing images. 74 © McGraw Hill LLC Because learning changes everything.® Biology Sylvia S. Mader Michael Windelspecht Chapter 10 Meiosis and Sexual Reproduction Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Outline 10.1 Overview of Meiosis 10.2 Genetic Variation 10.3 The Phases of Meiosis 10.4 Meiosis Compared to Mitosis 10.5 The Cycle of Life 10.6 Changes in Chromosome Number and Structure © McGraw Hill LLC 2 The Importance of Meiosis • It introduces an enormous amount of diversity. • There are more than 70 trillion different genetic combinations possible from the mating of two individuals. • Males and females differ in the way they form gametes. • In males, sperm production begins at puberty, but in the female, the process of producing eggs starts before birth and ends at menopause. © McGraw Hill LLC 3 10.1 Overview of Mitosis Special type of cell division. ■ Used only for sexual reproduction. Chromosomes are replicated in the S stage of interphase and then halved prior to fertilization. ■ Parents are diploid (2n). ■ Meiosis produces haploid (n) gametes. • Haploid cells contain a single set of chromosomes. • If there were no reduction of chromosomes in meiosis, the number of chromosomes would double each generation. ■ Gametes fuse in fertilization to form a diploid (2n) zygote. • The zygote becomes the next diploid (2n) generation. • If events in meiosis go wrong, gametes contain the wrong number of chromosomes. © McGraw Hill LLC 4 Homologous Pairs of Chromosomes In diploid body cells, chromosomes occur in pairs. Humans have 23 different types of chromosomes. Diploid (2n) cells have two chromosomes of each type. Chromosomes of the same type are said to be homologous chromosomes (homologues). • They have the same length. • Their centromeres are positioned in the same place. • One came from the father (the paternal homologue); the other from the mother (the maternal homologue). • When stained, they show similar banding patterns. © McGraw Hill LLC 5 Homologous Chromosomes Figure 10.1 Access the text alternative for slide images. © McGraw Hill LLC (a): L. Willatt/Science Source 6 Homologous Chromosomes and Alleles Homologous chromosomes have genes controlling the same trait at the same position. • Gene occurs in duplicate. • A maternal copy from the mother. • A paternal copy from the father. Many genes exist in several variant forms in a large population. Homologous copies of a gene may encode identical or different genetic information. The variants that exist for a gene are called alleles. An individual may have: • Identical alleles for a specific gene on both homologues (homozygous for the trait), or. • A maternal allele that differs from the corresponding paternal allele (heterozygous for the trait). • Example: a gene coding for short fingers on one homologue and a gene coding for long fingers at the same location on the other. © McGraw Hill LLC 7 Meiosis Is Reduction Division Meiosis involves two nuclear divisions. Meiosis I: Chromosomes are replicated prior to meiosis I. ■ Each chromosome consists of two identical sister chromatids. Homologous chromosomes pair up in synapsis. ■ Chromosomes may recombine or exchange genetic material. Homologous pairs align themselves against each other, side by side at the metaphase plate. The two members of a homologous pair separate. Each daughter cell receives one duplicated chromosome from each pair. ■ Chromosome number is reduced from 2n to n. Meiosis II: • DNA is not replicated between meiosis I and meiosis II. • Sister chromatids separate and move to opposite poles. • The four daughter cells contain one daughter chromosome from each pair. • Each daughter chromosome consists of a single chromatid. • The daughter cells are haploid. © McGraw Hill LLC 8 Overview of Meiosis 1 Figure 10.2 Access the text alternative for slide images. © McGraw Hill LLC 9 Overview of Meiosis 2 Figure 10.2 © McGraw Hill LLC Access the text alternative for slide images. 10 Overview of Meiosis 3 Figure 10.2 © McGraw Hill LLC 11 Overview of Meiosis 4 Figure 10.2 © McGraw Hill LLC 12 Overview of Meiosis © McGraw Hill LLC Figure 10.2 5 13 Overview of Meiosis 6 Figure 10.2 © McGraw Hill LLC Access the text alternative for slide images. 14 10.2 Genetic Variation Genetic variation is essential for a species to evolve and adapt in a changing environment. • Asexually reproducing organisms depend on mutations to generate variation in offspring. Meiosis brings about genetic variation in two key ways: • Crossing-over between homologous chromosomes, and. • Independent assortment of homologous chromosomes. Crossing-Over: It involves exchange of genetic material between nonsister chromatids during meiosis I. At synapsis, a nucleoprotein lattice (called the synaptonemal complex) appears between homologues. ■ Holds homologues together. ■ Aligns DNA of nonsister chromatids. ■ Allows crossing-over (exchange of genetic material) to occur. Then, homologues separate and are distributed to different daughter cells. © McGraw Hill LLC 15 Crossing-Over During Meiosis I Figure 10.3 Access the text alternative for slide images. © McGraw Hill LLC (a): Courtesy Dr. D. Von Wettstein 16 Independent Assortment of Homologous Chromosomes When homologous chromosome pairs align at the metaphase plate: ■ They separate in a random manner. ■ The maternal or paternal homologue may be oriented toward either pole of mother cell. It causes random mixing of blocks of alleles into gametes. The possible chromosome orientations for a cell with three pairs of homologous chromosomes is or 8, combinations of maternal and paternal chromosomes. © McGraw Hill LLC 17 Independent Assortment Figure 7.2 Access the text alternative for slide images. © McGraw Hill LLC 18 Fertilization and Crossing-Over Fertilization: union of male and female gametes. • Chromosomes donated by the parents are combined. • In humans, , or 4,951,760,200,000,000,000,000,000,000, genetically different zygotes are possible. Crossing-over may occur several times in each chromosome. © McGraw Hill LLC 19 Significance of Genetic Variation Asexual reproduction produces genetically identical clones. Sexual reproduction causes genetic recombinations among members of a population. ■ In humans with 23 pairs of chromosomes, the possible or 8,388,608, assuming no chromosomal combinations are crossing-over has occurred. Asexual reproduction is advantageous when the environment is stable. However, if the environment changes, genetic variability introduced by sexual reproduction may be advantageous. ■ Some offspring may have a better chance of survival. ■ Example: If the temperature rises due to climate change, an animal with less fur or reduced body fat would have an advantage. © McGraw Hill LLC 20 10.3 The Phases of Meiosis Meiosis I: Prophase I ■ A spindle forms. ■ The nuclear envelope fragments. ■ The nucleolus disappears. ■ Each chromosome is duplicated (consists of two identical sister chromatids). ■ Homologous chromosomes pair up and physically align themselves against each other side by side (synapsis). ■ Synapsed homologues are referred to as a bivalent (two homologues) or a tetrad (four chromatids). Metaphase I ■ Homologous pairs are arranged at the metaphase plate. ■ Bivalents are aligned at the spindle independently of one another. © McGraw Hill LLC 21 Meiosis I: Anaphase I and Telophase I Anaphase I ■ Homologous chromosomes of each bivalent separate from one another. ■ Homologues move towards opposite poles. ■ Sister chromatids do not separate. ■ Each is still a duplicated chromosome with two chromatids. • Reduction of chromosome number from 2n to n. Telophase I ■ Daughter cells have one duplicated chromosome (n) from each homologous pair. © McGraw Hill LLC 22 Meiosis I: Interkinesis Two haploid (n) daughter cells, each with one duplicated chromosome of each type. Interkinesis is similar to mitotic interphase, except. • It is usually shorter. • DNA replication does not occur. © McGraw Hill LLC 23 Meiosis II and Gamete Formation Prophase II – Chromosomes condense. Metaphase II – Chromosomes align at metaphase plate. ■ They are no longer in homologous pairs. Anaphase II. ■ Centromere dissolves. ■ Sister chromatids separate and become daughter chromosomes that are not duplicated. Telophase II and cytokinesis produce: ■ Four haploid (n) cells all genetically unique. ■ Gametes containing a mixture of maternal and paternal genes. © McGraw Hill LLC 24 Meiosis I and II Figures 10.5, 10.6 © McGraw Hill LLC Access the text alternative for slide images. 25 Meiosis I Figure 10.5 Access the text alternative for slide images. © McGraw Hill LLC 26 Meiosis II Figure 10.6 Access the text alternative for slide images. © McGraw Hill LLC 27 10.4 Meiosis Compared to Mitosis Meiosis • Requires two nuclear divisions. • Chromosomes synapse and cross-over. • Centromeres survive Anaphase I. • Halves chromosome number. • Produces four daughter nuclei. • Produces daughter cells genetically different from parent and each other. • Used only for sexual reproduction. Mitosis • Requires one nuclear division. • Chromosomes do not synapse or cross-over. • Centromeres dissolve in mitotic anaphase. • Preserves chromosome number. • Produces two daughter nuclei. • Produces daughter cells genetically identical to parent and to each other. • Used for asexual reproduction and growth. © McGraw Hill LLC 28 Meiosis I and Mitosis Similarities An orderly series of stages is involved in the sorting and division of chromosomes. The stages include prophase, prometaphase, metaphase, and telophase. Spindle fibers play an active role in sorting chromosomes. Cytokinesis follows the end of the process to divide cytoplasm between daughter cells. © McGraw Hill LLC 29 Meiosis I Compared to Mitosis Table 10.1 Meiosis I Compared to Mitosis Meiosis I Mitosis Prophase I Prophase Pairing of homologous chromosomes Metaphase I Bivalents at metaphase plate Anaphase I Homologues of each bivalent separate, and duplicated chromosomes move to poles Telophase I Two haploid daughter cells, not identical to the parent cell © McGraw Hill LLC No pairing of chromosomes Metaphase Duplicated chromosomes at metaphase plate Anaphase Sister chromatids separate, becoming daughter chromosomes that move to the poles Telophase Two diploid daughter cells, identical to the parent cell 30 Meiosis II Compared to Mitosis Table 10.2 Meiosis II Compared to Mitosis Meiosis II Mitosis Prophase II Prophase No pairing of chromosomes Metaphase II Haploid number of duplicated chromosomes at metaphase plate Anaphase II Sister chromatids separate, becoming daughter chromosomes that move to the poles Telophase II Four haploid daughter cells, not genetically identical © McGraw Hill LLC No pairing of chromosomes Metaphase Diploid number of duplicated chromosomes at metaphase plate Anaphase Sister chromatids separate, becoming daughter chromosomes that move to the poles Telophase Two diploid daughter cells, identical to the parent cell 31 Comparing Meiosis I and Mitosis Figure 10.7 Access the text alternative for slide images. © McGraw Hill LLC 32 10.5 The Cycle of Life A life cycle is all the reproductive events that occur from one generation to the next similar generation. In plants, haploid multicellular “individuals” alternate with diploid multicellular “individuals” (alternation of generations). The haploid individual: • Is called the gametophyte. • May be larger or smaller than the diploid individual. The diploid individual: • Is called the sporophyte. • May be larger or smaller than the haploid individual. Mosses are haploid for most of their life cycle. In fungi and most algae, only the zygote is diploid. Ferns and higher plants are diploid for most of their life cycles. In plants, algae, and fungi, gametes are produced by haploid individuals. © McGraw Hill LLC 33 Animal Life Cycle Animals are diploid and produce haploid gametes. The only haploid part of the life cycle is the gametes. The products of meiosis are always gametes. Meiosis occurs only during gametogenesis. • Production of sperm. • Spermatogenesis (in brief). • All four cells become sperm. • Production of eggs. • Oogenesis (in brief). • One of the four nuclei receives the majority of the cytoplasm. © McGraw Hill LLC • Becomes the egg or ovum. • Others wither away as polar bodies. 34 Human Life Cycle Sperm and egg are produced by meiosis in spermatogenesis and oogenesis. A sperm and egg fuse at fertilization. Results in a zygote. ■ The one-celled stage of an individual of the next generation. ■ Undergoes mitosis. It results in a multicellular embryo that gradually takes on features determined when the zygote was formed. All growth occurs as mitotic division. As a result of mitosis, each somatic cell in the body. ■ Has same number of chromosomes as zygote. ■ Has the same genetic makeup, which was determined when the zygote was formed. © McGraw Hill LLC 35 Spermatogenesis and Oogenesis in Humans Spermatogenesis: The testes contains stem cells called spermatogonia. ■ Spermatogonia make primary spermatocytes that undergo spermatogenesis. • Primary spermatocytes undergo meiosis I to form secondary spermatocytes. • Secondary spermatocytes undergo meiosis II to form four spermatids that differentiate to form sperm. Oogenesis: Ovaries contain stem cells called oogonia. ■ Oogonia produce primary oocytes. ■ Primary oocytes begin oogenesis, but only a few continue at sexual maturity of female. • Meiosis I of a primary oocyte forms a secondary oocyte and a polar body. • The secondary oocyte begins meiosis II but stops at metaphase II, leaves the ovary, and enters the uterine tube. • If there are no sperm in the uterine tube, the secondary oocyte degenerates. • If there are sperm in the uterine tube, it triggers the secondary oocyte to complete meiosis II and another polar body forms. © McGraw Hill LLC 36 Life Cycle of Humans 1 Figure 10.8 © McGraw Hill LLC 37 Life Cycle of Humans 2 Figure 10.8 © McGraw Hill LLC 38 Life Cycle of Humans 3 Figure 10.8 © McGraw Hill LLC 39 Life Cycle of Humans 4 Figure 10.8 © McGraw Hill LLC 40 Life Cycle of Humans 5 Figure 10.8 © McGraw Hill LLC 41 Life Cycle of Humans 6 Figure 10.8 Access the text alternative for slide images. © McGraw Hill LLC 42 Spermatogenesis and Oogenesis in Mammals Figure 10.9, 10.10 © McGraw Hill LLC Access the text alternative for slide images. 43 10.6 Changes in Chromosome Number and Structure Meiosis almost always proceeds normally. Euploidy is the correct number of chromosomes in a species. Aneuploidy is a change in the chromosome number. A karyotype is a display of chromosomes arranged by size, shape, and banding pattern for observing aneuploidies. Aneuploidy results from nondisjunction—failure of chromosomes to separate. ■ Nondisjunction can occur in meiosis I or meiosis II. ■ It may result in gain or loss of chromosomes. • Monosomy – only one of a particular type of chromosome. • Trisomy – three of a particular type of chromosome. © McGraw Hill LLC 44 Nondisjunction 1 Figure 10.11 © McGraw Hill LLC 45 Nondisjunction 2 Figure 10.11 © McGraw Hill LLC 46 Nondisjunction 3 Figure 10.11 © McGraw Hill LLC Access the text alternative for slide images. 47 Nondisjunction 4 Figure 10.11 © McGraw Hill LLC Access the text alternative for slide images. 48 Trisomies Trisomy occurs when an individual has three of a particular type of chromosome. • In humans, three autosomal trisomies are viable beyond birth. The most common autosomal trisomy seen among humans is trisomy 21. Also called Down syndrome. ■ The chance of a woman having a child with Down syndrome increases with her age. • The longer the oocytes are stored, the greater the chances of nondisjunction occurring. Recognized by these characteristics: ■ Short stature. ■ Eyelid fold. ■ Flat face. ■ Stubby fingers. ■ Wide gap between first and second toes. © McGraw Hill LLC 49 Trisomy 21 Figure 10.12 Access the text alternative for slide images. © McGraw Hill LLC (a): CNRI/Science Source 50 Changes in Sex Chromosome Number Results from inheriting too many or too few X or Y chromosomes. ■ Extra copies of sex chromosomes are more easily tolerated than autosomes. Nondisjunction during oogenesis or spermatogenesis. Turner syndrome (XO). ■ Female with a single X chromosome. ■ Short, with broad chest and widely spaced nipples. ■ Can be of normal intelligence and function with hormone therapy. © McGraw Hill LLC 51 Klinefelter Syndrome Klinefelter syndrome (XXY). ■ Male with underdeveloped testes and prostate; some breast overdevelopment. ■ Long arms and legs; large hands. ■ Near-normal intelligence unless XXXY, XXXXY, etc. ■ No matter how many X chromosomes are present, the presence of a chromosome Y renders the individual male. Deletion of the SRY gene results in XY female. ■ Lack of testis-determining factor, which plays a role in male genital development. ■ Presence of SRY determines maleness. © McGraw Hill LLC 52 Abnormal Sex Chromosome Number Figure 10.13 © McGraw Hill LLC (both): CNRI/Science Source 53 Changes in Chromosome Structure Environmental agents like radiation, organic chemicals, or certain viruses can cause chromosome breakage. • If broken ends of chromosomes don’t rejoin, mutations can occur. Changes in chromosome structure include: Deletion ■ One or both ends of a chromosome breaks off. ■ Two simultaneous breaks lead to loss of an internal segment. Duplication ■ There is presence of a chromosomal segment more than once in the same chromosome. Translocation ■ A segment from one chromosome moves to a nonhomologous chromosome. ■ It follows breakage of two nonhomologous chromosomes and improper reassembly. © McGraw Hill LLC 54 Inversion • It occurs as a result of two breaks in a chromosome. • The internal segment is reversed before re-insertion. • Genes occur in reverse order in the inverted segment. © McGraw Hill LLC 55 Deletion and Translocation Syndromes Changes in chromosome structure can cause various syndromes and can be detected in a karyotype or by studying an inheritance pattern in a family. ■ Deletion syndromes. • Williams syndrome is a loss of the end of chromosome 7, which contains the gene for elastin. • Children have turned-up noses, wide mouths, a small chin, and large ears. ■ Translocation syndromes. • Chronic myeloid leukemia, a blood cancer, is caused by a translocation between chromosomes 22 and 9. • Alagille syndrome is a translocation between chromosomes 2 and 20, which can lead to a congenital heart defect called tetralogy of Fallot. © McGraw Hill LLC 56 Types of Chromosomal Mutations Figure 10.14 © McGraw Hill LLC Access the text alternative for slide images. 57 Deletion Figure 10.15 Access the text alternative for slide images. © McGraw Hill LLC (b): Courtesy The Williams Syndrome Association 58 Chronic Myeloid Leukemia Figure 10.16 © McGraw Hill LLC Jean Secchi/Dominique Lecaque/Roussel-Uclaf/CNRI/Science Source 59 Because learning changes everything.® www.mheducation.com Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Accessibility Content: Text Alternatives for Images © McGraw Hill LLC 61 Homologous Chromosomes – Text Alternative Return to parent-slide containing images. A) A set of 22 pairs of chromosomes with XX as twenty third pair. B) Homologous pair of paternal and maternal chromosomes: Paternal chromosome: It shows a blue colored chromosome with a centromere in the center which on duplication forms two nonsister chromatids with two kinetochore. Maternal chromosome: It shows a red colored chromosome which on duplication forms two sister chromatids. Return to parent-slide containing images. 62 © McGraw Hill LLC Overview of Meiosis – Text Alternative 1 Return to parent-slide containing images. Following DNA replication, each chromosome is duplicated and consists of two chromatids. During meiosis I, homologous chromosomes pair and separate. During meiosis II, the sister chromatids of each duplicated chromosome separate. At the completion of meiosis, there are four haploid daughter cells. Each daughter cell has one of each kind of chromosome. Return to parent-slide containing images. 63 © McGraw Hill LLC Overview of Meiosis – Text Alternative 2 Return to parent-slide containing images. The labels on the diagram include centromere, nucleolus, centrioles, homologous chromosome pair, and homologous chromosome pair. Return to parent-slide containing images. 64 © McGraw Hill LLC Overview of Meiosis – Text Alternative 6 Return to parent-slide containing images. The nucleolus of cell shows longitudinal homologous chromosome pair with a centromere in their centers with centrioles outside the nucleolus where 2n equals 4. After DNA replication, synapsis takes place forming sister chromatids, where 2n equals 4. The data for Meiosis one and two are as follows: Meiosis one: Homologues synapse and then separate. Meiosis two: Sister chromatids separate, becoming daughter chromosomes (each cell with n equals 2). Return to parent-slide containing images. 65 © McGraw Hill LLC Crossing-Over During Meiosis I – Text Alternative Return to parent-slide containing images. A. B. C. D. The homologous chromosomes pair up, and a nucleoprotein lattice develops between them. This is an electron micrograph of the lattice. It “zippers” the members of the bivalent together, so that corresponding genes on paired chromosomes are in alignment. This visual representation shows only two places where nonsister chromatids 1 and 3 have come in contact. Chiasmata indicate where crossing-over has occurred. The exchange of color represents the exchange of genetic material. Following meiosis II, daughter chromosomes have a new combination of genetic material due to crossing-over, which occurred between nonsister chromatids during meiosis I. Return to parent-slide containing images. 66 © McGraw Hill LLC Independent Assortment – Text Alternative Return to parent-slide containing images. When a parent cell has three pairs of homologous chromosomes, there are 23, or 8, possible chromosome alignments at the metaphase plate due to independent assortment. Each possible combination is shown, one in each cell. Return to parent-slide containing images. 67 © McGraw Hill LLC Meiosis I and II – Text Alternative Return to parent-slide containing images. The details of Meiosis 1 are: Prophase I :Homologous chromosomes pair during synapsis. Metaphase I: Homologous chromosome pairs align at the metaphase plate. Anaphase I: Homologous chromosomes separate, pulled to opposite poles by centromeric spindle fibers. Telophase I: Daughter cells have one chromosome from each homologous pair. Interkinesis: Chromosomes still consist of two chromatids. The details of meiosis where cells from meiosis one have n equals 2) are as follows. Prophase two: Cells have one chromosome from each homologous pair. Metaphase two: Chromosomes align at the metaphase plate. Anaphase two: Daughter chromosomes move toward the poles. Telophase two: Spindle disappears, nuclei form, and cytokinesis takes place, where n equals 2. Daughter cells: Meiosis results in four haploid daughter cells. Return to parent-slide containing images. 68 © McGraw Hill LLC Meiosis I – Text Alternative Return to parent-slide containing images. More detailed descriptions of the stages of Meiosis I are as follows. Prophase I :Homologous chromosomes pair during synapsis. Metaphase I: Homologous chromosome pairs align at the metaphase plate. Anaphase I: Homologous chromosomes separate, pulled to opposite poles by centromeric spindle fibers. Telophase I: Daughter cells have one chromosome from each homologous pair. Interkinesis: Chromosomes still consist of two chromatids. Return to parent-slide containing images. 69 © McGraw Hill LLC Meiosis II – Text Alternative Return to parent-slide containing images. The data for stages of meiosis two (where cells from meiosis one have n equals 2) are as follows. Prophase two: Cells have one chromosome from each homologous pair. Metaphase two: Chromosomes align at the metaphase plate. Anaphase two: Daughter chromosomes move toward the poles. Telophase two: Spindle disappears, nuclei form, and cytokinesis takes place, where n equals 2. Daughter cells: Meiosis results in four haploid daughter cells. Return to parent-slide containing images. 70 © McGraw Hill LLC Comparing Meiosis I and Mitosis – Text Alternative Return to parent-slide containing images. Why does meiosis produce daughter cells with half the number of chromosomes, whereas mitosis produces daughter cells with the same number of chromosomes as the parent cell? Compare metaphase I of meiosis to metaphase of mitosis. Only in metaphase I of meiosis are the homologous chromosomes paired at the metaphase plate. Members of homologous chromosome pairs separate during anaphase I, and therefore the daughter cells are haploid. The exchange of color between nonsister chromatids represents the crossing-over that occurred during meiosis I. The blue chromosomes were inherited from the paternal parent, and the red chromosomes were inherited from the maternal parent. Return to parent-slide containing images. 71 © McGraw Hill LLC Life Cycle of Humans – Text Alternative 6 Return to parent-slide containing images. Meiosis in males is a part of sperm production, and meiosis in females is a part of egg production. When a haploid sperm fertilizes a haploid egg, the zygote is diploid. The zygote undergoes mitosis as it develops into a newborn child. Mitosis continues throughout life during growth and repair. Return to parent-slide containing images. 72 © McGraw Hill LLC Spermatogenesis and Oogenesis in Mammals – Text Alternative Return to parent-slide containing images. The details of spermatogenesis are: he data is as follows: Meiosis one: primary spermatocyte (with 2n). Meiosis two: secondary spermatocytes (with n). Metamorphosis and maturation: sperm (with n). The details of oogenesis are: Meiosis 1: primary oocyte (2n) leads to first polar body (n) and secondary oocyte (n). Meiosis 2 is completed after entry of sperm fertilization. Fertilization egg (n) combines with sperm (n nucleus) to give zygote (2n) as a result of fusion of sperm and egg nucleus. Return to parent-slide containing images. 73 © McGraw Hill LLC Nondisjunction – Text Alternative 3 Return to parent-slide containing images. A) Meiosis One: Pair of homologous chromosomes get nondisjunctioned. Meiosis two: Pair of homologous chromosomes in one egg with another abnormal egg. Fertilization: Occurs in two eggs with pair of homologous chromosomes and two abnormal eggs. Zygote: Four eggs formed with diploid number of chromosomes as 2n plus 1, 2n plus 1, 2n minus 1 and 2n minus 1. Return to parent-slide containing images. 74 © McGraw Hill LLC Nondisjunction – Text Alternative 4 Return to parent-slide containing images. A. B. Meiosis One: Pair of homologous chromosomes get nondisjunctioned. Meiosis two: Pair of homologous chromosomes in one egg with another abnormal egg. Fertilization: Occurs in two eggs with pair of homologous chromosomes and two abnormal eggs. Zygote: Four eggs formed with diploid number of chromosomes as 2n plus 1, 2n plus 1, 2n minus 1 and 2n minus 1. Meiosis One: Pair of homologous chromosomes are present in the normal egg. Meiosis two: Normal division of egg into two eggs occur, where second egg is nondisjunctioned. Fertilization: Occurs in four newly created eggs (where first and second eggs are normal, while the third egg has a pair of chromosomes present in it and fourth egg is abnormal). Zygote: Four eggs formed with diploid number of chromosomes as 2n, 2n, 2n plus 1 and 2n plus 1. Return to parent-slide containing images. 75 © McGraw Hill LLC Trisomy 21 – Text Alternative Return to parent-slide containing images. A. B. Persons with Down syndrome, or trisomy 21, have an extra chromosome 21. The karyotype of an individual with Down syndrome shows three copies of chromosome 21. Therefore, the individual has three copies instead of two copies of each gene on chromosome 21. An extra copy of the Gart gene, which leads to high levels of purine in the blood, accounts for many of the characteristics of Down syndrome. Return to parent-slide containing images. 76 © McGraw Hill LLC Types of Chromosomal Mutations – Text Alternative Return to parent-slide containing images. A. B. C. D. Deletion is the loss of a chromosome piece. Duplication occurs when the same piece is repeated within the chromosome. Inversion occurs when a piece of chromosome breaks loose and then rejoins in the reversed direction. Translocation is the exchange of chromosome pieces between nonhomologous pairs. Return to parent-slide containing images. 77 © McGraw Hill LLC Deletion – Text Alternative Return to parent-slide containing images. A. B. When chromosome 7 loses an end piece, the result is Williams syndrome. These children, although unrelated, have the same appearance, health, and behavioral problems. Return to parent-slide containing images. 78 © McGraw Hill LLC Because learning changes everything.® Biology Sylvia S. Mader Michael Windelspecht Chapter 11 Mendelian Patterns of Inheritance Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Outline 11.1 Gregor Mendel 11.2 Mendel’s Laws 11.3 Mendelian Patterns of Inheritance and Human Disease 11.4 Beyond Mendelian Inheritance © McGraw Hill LLC 2 11.1 Gregor Mendel Parents of contrasting appearance produce offspring of intermediate appearance: blending concept of inheritance. • Over time, variation would decrease as individuals became more alike in their traits. Blending was a popular concept during Mendel’s time. Mendel’s findings were in contrast with this. He formulated the particulate theory of inheritance. Mendel proposed the laws of segregation and independent assortment. • Inheritance involves reshuffling of genes from generation to generation. © McGraw Hill LLC 3 Gregor Mendel’s Background Austrian monk ○ Studied science and mathematics at the University of Vienna. ○ Conducted breeding experiments with the garden pea Pisum sativum. ○ Carefully gathered and documented mathematical data from his experiments. Formulated fundamental laws of heredity in the early 1860s ○ Had no knowledge of cells or chromosomes. ○ Did not have a microscope. ○ Experiments on the inheritance of simple traits in the garden pea disproved the blending hypothesis. © McGraw Hill LLC 4 Mendel Worked with the Garden Pea The garden pea: Organism used in Mendel’s experiments. A good choice for several reasons: ○ Easy to cultivate. ○ Short generation. ○ Normally self-pollinating, but can be cross-pollinated by hand. ○ Pollen was transferred from the male (anther) of one plant to the female (stigma) parts of another plant. ○ True-breeding varieties available. ○ Simple, objective traits. © McGraw Hill LLC 5 Cross-Pollination in the Garden Pea 1 Figure 11.2 © McGraw Hill LLC 6 Cross-Pollination in the Garden Pea 2 Figure 11.2 © McGraw Hill LLC 7 11.2 Mendel’s Laws © McGraw Hill LLC 8 Single-Trait Cross Done by Mendel 1 Figure 11.3 © McGraw Hill LLC 9 Single-Trait Cross Done by Mendel 2 Figure 11.3 © McGraw Hill LLC 10 Single-Trait Cross Done by Mendel 3 Figure 11.3 © McGraw Hill LLC 11 Single-Trait Cross Done by Mendel 4 Figure 11.3 Access the text alternative for slide images. © McGraw Hill LLC 12 Relationship Between Observed Phenotype and F2 Offspring Figure 11.4 Access the text alternative for slide images. © McGraw Hill LLC 13 Law of Segregation • Each individual has a pair of factors (alleles) for each trait. • The factors (alleles) segregate (separate) during gamete (sperm and egg) formation. • Each gamete contains only one factor (allele) from each pair of factors. • Fertilization gives the offspring two factors for each trait. © McGraw Hill LLC 14 Mendel’s Cross as Viewed by Modern Genetics Each trait in a pea plant is controlled by two alleles (alternate forms of a gene). Dominant allele (capital letter) masks the expression of the recessive allele (lowercase). Alleles occur on a homologous pair of chromosomes at a particular gene locus. • Homozygous = identical alleles • Heterozygous = different alleles © McGraw Hill LLC 15 Homologous Chromosomes Figure 11.5 Access the text alternative for slide images. © McGraw Hill LLC 16 Genotype Versus Phenotype Genotype • It refers to the two alleles an individual has for a specific trait. • If identical, genotype is homozygous. • If different, genotype is heterozygous. Phenotype • It refers to the physical appearance of the individual. © McGraw Hill LLC 17 Dominant and Recessive Alleles The dominant and recessive alleles represent DNA sequences that code for proteins. The dominant allele codes for the protein associated with the normal gene function within the cell. The recessive allele represents a “loss of function.” During meiosis I, the homologous chromosomes separate. • The two alleles separate from each other. • The process of meiosis explains Mendel’s law of segregation and why only one allele for each trait is in a gamete. © McGraw Hill LLC 18 Mendel’s Law of Independent Assortment © McGraw Hill LLC 19 Dihybrid Cross Done by Mendel Figure 11.6 Access the text alternative for slide images. © McGraw Hill LLC 20 Independent Assortment and Segregation During Meiosis 1 Parent cell has two pairs of homologous chromosomes. Figure 11.7 © McGraw Hill LLC 21 Independent Assortment and Segregation During Meiosis 2 Figure 11.7 © McGraw Hill LLC 22 Independent Assortment and Segregation During Meiosis 3 Figure 11.7 Access the text alternative for slide images. © McGraw Hill LLC 23 Independent Assortment and Segregation During Meiosis 4 Figure 11.7 Access the text alternative for slide images. © McGraw Hill LLC 24 Mendel and the Laws of Probability Punnett square: table listing all possible genotypes resulting from a cross. • All possible sperm genotypes are lined up on one side. • All possible egg genotypes are lined up on the other side. • All possible zygote genotypes are placed within the squares. © McGraw Hill LLC 25 Punnett Square • It allows us to easily calculate probability of genotypes and phenotypes among the offspring. • Punnett square in next slide shows a 50% (or ) chance. • The chance of • The chance of An offspring will inherit • The chance of • The chance of • The chance of • The chance of The sum rule allows us to add the genotypes that produce the identical phenotype to find out the chance of a particular phenotype. © McGraw Hill LLC 26 Punnett Square Example Figure 11.8 Access the text alternative for slide images. © McGraw Hill LLC 27 Testcrosses Individuals with recessive phenotype always have the homozygous recessive genotype. However, individuals with dominant phenotype have indeterminate genotype. • May be homozygous dominant, or. • Heterozygous. A testcross determines the genotype of an individual having the dominant phenotype. © McGraw Hill LLC 28 One-Trait Testcrosses Figure 11.9 Access the text alternative for slide images. © McGraw Hill LLC 29 Two-Trait Testcross • An individual with both dominant phenotypes is crossed with an individual with both recessive phenotypes. • If the individual with the dominant phenotypes is heterozygous for both traits, the expected phenotypic ration is 1:1:1:1. © McGraw Hill LLC 30 11.3 Mendelian Patterns of Inheritance and Human Disease Genetic disorders are medical conditions caused by alleles inherited from parents. Autosome is any chromosome other than a sex chromosome (X or Y). Genetic disorders caused by genes on autosomes are called autosomal disorders. Some genetic disorders are autosomal dominant. • An individual with AA has the disorder. • An individual with Aa has the disorder. • An individual with aa does NOT have the disorder. Other genetic disorders are autosomal recessive. • An individual with AA does NOT have the disorder. • An individual with Aa does NOT have the disorder, but is a carrier. • An individual with aa DOES have the disorder. © McGraw Hill LLC 31 Autosomal Recessive Pedigree Figure 11.10 Access the text alternative for slide images. © McGraw Hill LLC 32 Autosomal Recessive Disorders If both parents carry one copy of a recessive gene they are unaffected but are capable of having a child with two copies of the gene who is affected. Methemoglobinemia. • It is a relatively harmless disorder. • Accumulation of methemoglobin in the blood causes skin to appear bluish-purple. Cystic Fibrosis • Mucus in bronchial tubes and pancreatic ducts is particularly thick and viscous. © McGraw Hill LLC 33 Methemoglobinemia Figure 11.11 © McGraw Hill LLC Courtesy Division of Medical Toxicology, University of Virginia 34 Cystic Fibrosis Figure 11.12 Access the text alternative for slide images. © McGraw Hill LLC 35 Autosomal Dominant Disorders Two parents with a dominantly inherited disorder will be affected by one copy of the gene. • It is possible for them to have unaffected children. • Osteogenesis Imperfecta. • Characterized by weakened, brittle bones. • Most cases are caused by mutation in genes required for the synthesis of type I collagen. • Huntington Disease. • Neurological disease that leads to progressive degeneration of brain cells. • Caused by mutated copy of the gene for a protein called huntingtin. • Hereditary Spherocytosis. • It is caused by a mutation in the ankyrin-1 gene. • Red blood cells become spherical, are fragile, and burst easily. © McGraw Hill LLC 36 Autosomal Dominant Pedigree Figure 11.13 Access the text alternative for slide images. © McGraw Hill LLC 37 11.4 Beyond Mendelian Inheritance Some traits are controlled by multiple alleles (multiple allelic traits). The gene exists in several allelic forms, but each individual only has two alleles. ABO blood types: The alleles: • antigen on red blood cells, anti-B antibody in plasma. • antigen on red blood cells, anti-A antibody in plasma. • i = Neither A nor B antigens on red blood cells, both anti-A and anti-B antibodies in plasma. The ABO blood type is also an example of codominance. • More than one allele is fully expressed. • Both and are expressed in the presence of the other. © McGraw Hill LLC 38 ABO Blood Type Access the text alternative for slide images. © McGraw Hill LLC 39 Incomplete Dominance Heterozygote has a phenotype intermediate between that of either homozygote. • Homozygous red has red phenotype. • Homozygous white has white phenotype. • Heterozygote has pink (intermediate) phenotype. Phenotype reveals genotype without a testcross. © McGraw Hill LLC 40 Incomplete Dominance Results Figure 11.14 Access the text alternative for slide images. © McGraw Hill LLC 41 Familial Hypercholesterolemia (FH) ■ Homozygotes for the mutant allele develop fatty deposits in the skin and tendons and may have heart attacks during childhood. ■ Heterozygotes may suffer heart attacks during early adulthood. ■ Homozygotes for the normal allele do not have the disorder. © McGraw Hill LLC 42 Incomplete Penetrance The dominant allele may not always lead to the dominant phenotype in a heterozygote. Many dominant alleles exhibit varying degrees of penetrance. Example: polydactyly. • There are extra digits on hands, feet, or both. • Not all individuals who inherit the dominant polydactyly allele will exhibit the trait. © McGraw Hill LLC 43 Pleiotropic Effects Pleiotropy occurs when a single mutant gene affects two or more distinct and seemingly unrelated traits. Marfan syndrome has been linked to a mutated gene FBN1 on chromosome 15 which codes for the fibrillin protein. Marfan syndrome is pleiotropic and results in the following phenotypes: • Disproportionately long arms, legs, hands, and feet • A weakened aorta • Poor eyesight © McGraw Hill LLC 44 Marfan Syndrome Figure 11.15 Access the text alternative for slide images. © McGraw Hill LLC 45 Polygenic Inheritance Occurs when a trait is governed by two or more sets of alleles. Each dominant allele has a quantitative effect on the phenotype. • These effects are additive. It results in continuous variation of phenotypes within a population. The traits may also be affected by the environment. Examples • Human skin color • Height • Eye color © McGraw Hill LLC 46 Polygenic Inheritance Example Figure 11.17 Access the text alternative for slide images. © McGraw Hill LLC 47 X and Y Chromosomes In mammals. • The X and Y chromosomes determine gender. • Females are XX. • Males are XY. © McGraw Hill LLC 48 X-Linked Inheritance The term X-linked is used for genes that have nothing to do with gender. • X-linked genes are carried on the X chromosome. • The Y chromosome does not carry these genes. • It was discovered in the early 1900s by a group at Columbia University, headed by Thomas Hunt Morgan. • Performed experiments with fruit flies • They can be easily and inexpensively raised in simple laboratory glassware. • Fruit flies have a similar sex chromosome pattern to humans. • Morgan’s experiments with X-linked genes apply directly to humans. © McGraw Hill LLC 49 The Polygenic Basis of Skin Color Figure 11.18 Access the text alternative for slide images. © McGraw Hill LLC 50 Fruit Flies and X-Linked Inheritance Figure 11.19 Access the text alternative for slide images. © McGraw Hill LLC 51 Human X-Linked Disorders Color blindness. • The allele for the blue-sensitive protein is autosomal. • The alleles for the red- and green-sensitive pigments are on the X chromosome. Menkes syndrome. • It is caused by a defective allele on the X chromosome. • It disrupts movement of the metal copper in and out of cells. • Phenotypes include brittle hair, poor muscle tone, seizures, and low body temperature, skeletal anomalies. Muscular dystrophy. • Causes wasting away of the muscle. • It is caused by the absence of the muscle protein dystrophin. Adrenoleukodystrophy. • It is an X-linked recessive disorder. • It is a failure of a carrier protein to move either an enzyme or very long-chain fatty acid into peroxisomes. Hemophilia. • It is an absence or minimal presence of clotting factor VIII or clotting factor IX. • An affected person’s blood either does not clot or clots very slowly. © McGraw Hill LLC 52 X-Linked Recessive Pedigree Figure 11.20 Access the text alternative for slide images. © McGraw Hill LLC 53 Because learning changes everything.® www.mheducation.com Copyright 2022 © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC. Accessibility Content: Text Alternatives for Images © McGraw Hill LLC 55 Single-Trait Cross Done by Mendel – Text Alternative 4 Return to parent-slide containing images. The data is as follows: P generation tall pea plant (TT) crosses with short plant (tt), P gametes (T and t) form F sub 1 generation (Tt). The data for cross of F sub 1 gametes with F sub 2 generation using eggs and sperms are as follows: Sperm (T): egg (T): TT (tall) Sperm (t): egg (T): Tt (tall) Sperm (T): egg (t): Tt (tall) Sperm (t): egg (t): Tt (short). Return to parent-slide containing images. 56 © McGraw Hill LLC Relationship Between Observed Phenotype and F2 Offspring – Text Alternative Return to parent-slide containing images. The data for trait, characteristics (dominant and recessive), F sub 2 results (dominant, recessive, ratio) are as follows: Stem length: Tall: Short: 787: 277: (2.84:1) Pod shape: Inflated: Constricted: 882: 299: (2.95:1) Seed shape: Round: Wrinkled: 5474: 1850: (2.96:1) Seed color: Yellow: Green: 6022: 2001: (3.01:1) Flower position: Axial: Terminal: 651: 207: (3.14:1) Flower color: Purple: White: 705: 224: (3.15:1) Flower color: Green: Yellow: 428: 152: (2.82:1) Blank: Blank: Blank: Totals: 14949: 5010: (2.98:1). Return to parent-slide containing images. 57 © McGraw Hill LLC Homologous Chromosomes – Text Alternative Return to parent-slide containing images. A. Homologous chromosomes have alleles for the same genes at specific loci. Alternative forms of the gene are represented by capital versus lower case letters. B. B. sister chromatids of duplicated chromosomes have the same alleles for each gene. Return to parent-slide containing images. 58 © McGraw Hill LLC Dihybrid Cross Done by Mendel – Text Alternative Return to parent-slide containing images. The data is as follows: P generation tall green plant (TTGG) crosses with short yellow plant (ttgg), P gametes (TG and tg) form F sub 1 generation (TtGg). The data for cross of F sub 1 gametes with F sub 2 generation using eggs and sperms are as follows: Sperm (TG): egg (TG): TTGG (tall plant and green pod). Sperm (TG): egg (Tg): TTGg (tall plant and green pod). Sperm (TG): egg (tG): TtGG (tall plant and green pod). Sperm (TG): egg (tg): TtGg (tall plant and green pod). Sperm (Tg): egg (TG): TTGg (tall plant and green pod. Sperm (Tg): egg (Tg): TTgg (tall plant and yellow pod). Sperm (Tg): egg (tG): TtGg (tall plant and green pod). Sperm (Tg): egg (tg): TtGg (tall plant and yellow pod). Sperm (tG): egg (TG): TtGG (tall plant and green pod). Sperm (tG): egg (Tg): TtGg (tall plant and green pod). Sperm (tG): egg (tG): ttGG (short plant and green pod). Sperm (tG): egg (tg): ttGg (short plant and green pod). Sperm (tg): egg (TG): TtGg (tall plant and green pod). Sperm (tg): egg (Tg): Ttgg (tall plant and yellow pod). Sperm (tg): egg (tG): ttGg (short plant and green pod). Sperm (tg): egg (tg): ttgg (short plant and yellow pod). Return to parent-slide containing images. 59 © McGraw Hill LLC Independent Assortment and Segregation During Meiosis – Text Alternative 3 Return to parent-slide containing images. The parent cell having two pairs of homologous chromosomes shows leads to All orientations of homologous chromosomes are possible at metaphase I in keeping with the law of independent assortment, which further leads to metaphase 2, each daughter cell has only one member of each homologours pair in keeping with the law of seggregation. Return to parent-slide containing images. 60 © McGraw Hill LLC Independent Assortment and Segregation During Meiosis – Text Alternative 4 Return to parent-slide containing images. In the example, the parent cell has two pairs of homologous chromosomes. All orientations of homologous chromosomes are possible at metaphase I in keeping with the law of independent assortment. At metaphase II, each daughter cell has only one member of each homologous pair in keeping with the law of segregation. All possible combinations of chromosomes and alleles occur in the gametes as suggested by Mendel’s two laws. Return to parent-slide containing images. 61 © McGraw Hill LLC Punnett Square Example – Text Alternative Return to parent-slide containing images. The data is as follows: Parents with each (Aa) gamete cross with each other forming offsprings using eggs and sperms as follows: Sperm (A): egg (A): Offspring AA (normal pigmentation). Sperm (A): egg (a): Offspring Aa (normal pigmentation). Sperm (a): egg (A): Offspring Aa (normal pigmentation). Sperm (a): egg (a): Offspring aa (albino: no pigmentation). The allele key reads: A, normal pigmentation; a, lack of pigmentation. Phenotypic ratio: 3 normal pigmentation and 1 albino (no pigmentation). Return to parent-slide containing images. 62 © McGraw Hill LLC One-Trait Testcrosses – Text Alternative Return to parent-slide containing images. A) Heterozygous dominant phenotype: Tt crosses tt: The data for cross of F sub 1 gametes with F sub 2 generation using eggs and sperms are as follows: Sperm (T): egg (t): offspring (Tt) (tall). Sperm (t): egg (t): offspring (tt) (short). Allele key: T, tall plant and t, short plant. Phenotypic ratio: 1 tall and 1 short. B) Homozygous dominant phenotype: Tt crosses tt: The data for cross of F sub 1 gametes with F sub 2 generation using eggs and sperms are as follows: Sperm (T): egg (t): offspring (Tt) (tall). Allele key: T, tall plant and t, short plant. Phenotypic ratio: All tall plants. Return to parent-slide containing images. 63 © McGraw Hill LLC Autosomal Recessive Pedigree – Text Alternative Return to parent-slide containing images. Pedigree for autosomal recessive disorders shows the following data: One affected female in first generation, one affected female and male in fourth generation. Two carrier (unaffected) females in second generation and two carrier (unaffected) males and males in third generation. One unaffected (one allele unknown) male of first generation, two males of second generation, a female and a male of third generation and a female of fourth generation. Autosomal recessive disorders: Most affected children have unaffected parents. Heterozygotes (Aa) have an unaffected phenotype. Two affected parents will always have affected children. Close relatives who reproduce are more likely to have affected children. Both males and females are affected with equal frequency. Return to parent-slide containing images. 64 © McGraw Hill LLC Cystic Fibrosis – Text Alternative Return to parent-slide containing images. Chloride ions and water are trapped inside the cell; a defective chloride ion channel does not allow chloride ions to pass through; the lumen of the respiratory tract fills with thick, sticky mucus. Return to parent-slide containing images. 65 © McGraw Hill LLC Autosomal Dominant Pedigree – Text Alternative Return to parent-slide containing images. Pedigree for autosomal dominant disorders shows the following data: One affected female and male in first generation, one affected female and one affected (one allele unknown) male in second generation and one affected female and male in third generation. Three females and a male in second generation and three females and a male in third generation are unaffected. Autosomal dominant recessive: • Affected children will usually have an affected parent. • Heterozygotes (Aa) are affected. • Two affected parents can produce an unaffected child. • Two unaffected parents will not have affected children. • Both males and females are affected with equal frequency. Return to parent-slide containing images. 66 © McGraw Hill LLC ABO Blood Type – Text Alternative Return to parent-slide containing images. The data is given as follows: A: I sup A I sup A, I sup A lowercase i; B: I sup B I sup B, I sup B lowercase I; AB: I sup A I sup B; and O: lowercase I lowercase i. Return to parent-slide containing images. 67 © McGraw Hill LLC Incomplete Dominance Results – Text Alternative Return to parent-slide containing images. Red flower genotype: capital R sub 1 capital R sub 1. Pink flower genotype: capital R sub 1 capital R sub 2. White flower genotype: capital R sub 1 capital R sub 2. When two pink flowers are bred, the resulting offspring are: 1 red, 2 pink, 1 white. Return to parent-slide containing images. 68 © McGraw Hill LLC Marfan Syndrome – Text Alternative Return to parent-slide containing images. The data for connective tissue defects are as follows: Marfan syndrome impact the skeleton: Chest wall deformities, long, thin fingers, arms, legs, scoliosis (curvature of the spine), flat feet, long, narrow face and loose joints. Heart and blood vessels: Mitral valve prolapse and enlargement of aorta (aneurysm, aortic wall tear). Eyes: Lens dislocation, severe nearsightedness. Heart and blood vessels. Skeleton. Lungs: Collapsed lungs. Skin: Stretch marks, recurrent hernias, dural ectasia, stretching of the membrane that holds spinal fluid. Return to parent-slide containing images. 69 © McGraw Hill LLC Polygenic Inheritance Example – Text Alternative Return to parent-slide containing images. P generation: Six non solid dots cross with six solid dots. F sub 1 generation: Six dots (three nonsolid, three solid) cross with six dots (three nonsolid, three solid) resulting in six dots (all six non solid), six dots (five non solid, one solid), six dots (four non solid, two solid), six dots (three non solid, three solid), six dots (two non solid, five solid) and six dots (one non solid, six solid), six dots (all six solid). The horizontal axis of bar graph represents genotype examples, while the vertical axis represents proportion of population. The data is as follows: aabbcc: 1 over 64. Aabbcc: 6 over 64. AaBbcc: Little lesser than 15 over 64. AaBbCc: 20 over 64. AABbCc: Little lesser than 15 over 64 AABBCc: 6 over 64. AABBCC: 1 over 64. A parabolic curve passes through the mean all bars. Return to parent-slide containing images. 70 © McGraw Hill LLC The Polygenic Basis of Skin Color – Text Alternative Return to parent-slide containing images. The horizontal axis of represents genotype examples, while the vertical axis represents proportion of population. The data is as follows: 0: aabbcc 1: Aabbcc, aaBbcc and aabbCc 2: AaBbcc, AabbCc, aaBbCc, Aabbcc, aaBBcc and aabbCC. 3: AaBbCc, aaBbCC, AAbbCc, AabbCC, AABbcc, aaBBCc and AaBBcc. 4: aaBBCC, AAbbCC, AABBcc, AaBbCC, AaBBCc and AABbCc. 5: AaBBCC, AABbCC and AABBCc. 6: AABBCC. Return to parent-slide containing images. 71 © McGraw Hill LLC Fruit Flies and X-Linked Inheritance – Text Alternative Return to parent-slide containing images. The data is as follows: P generation of housefly (X sup r Y: white eyes) crosses with housefly (X sup R X sup R: red eyes), P gametes (X sup r and X sup R) form F sub 1 generation (X sup R Y and X sup R X sup r). The data for cross of F sub 1 gametes with F sub 2 generation using eggs and sperms are as follows: Sperm (X sup R): egg (X sup R): X sup R X sup R (all red-eyed). Sperm (X sup R): egg (X sup r): X sup R X sup r (red-eyed). Sperm (y): egg (X sup R): X sup R Y (red-eyed). Sperm (y): egg (X sup r): X sup r Y (white eyed). Allele key: X sup uppercase R, red eyes; and X sup lowercase R, white eyes. Phenotypic ratio: females, all red eyed; and males 1 red-eyed and 1 white-eyed. Return to parent-slide containing images. 72 © McGraw Hill LLC X-Linked Recessive Pedigree – Text Alternative Return to parent-slide containing images. Pedigree for X-linked recessive disorders shows the following data: One color-blind grandfather (X sup b Y) in first generation, one color-blind daughter (X sup b X sup b) in second generation, two color-blind grandsons (X sup b Y) in third generation. A carrier daughter (X sup B X sup b) in second generation. Two unaffected males in second generation, one unaffected and two unaffected females in third generation. X-linked recessive disorders: • More males than females are affected. • An affected son can have parents who have the normal phenotype. • For a female to have the characteristic, her father must also have it. Her mother must have it or be a carrier. • The characteristic often skips a generation from the grandfather to the grandson. • If a woman has the characteristic, all of her sons will have it. Return to parent-slide containing images. 73 © McGraw Hill LLC