Cell Division Lecture Outline PDF

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Because learning changes everything. ® INQUIRY INTO LIFE Seventeenth Edition Sylvia S. Mader Michael Windelspecht Chapter 05 Cell Division Lecture Outline © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  5.1 The Cell Cycle 1 Cell division enables a single-celled fertilized egg to grow into an organism with trillions of cells. Somatic cells are the body cells that continue to undergo cell division even as an adult. Thousands of new blood cells, skin cells, and cells that line the digestive and respiratory tracts are produced every day. © McGraw Hill LLC 2  5.1 The Cell Cycle 2 Apoptosis is programmed cell death. Decreases number of cells. Occurs during development to remove unwanted tissue. Tail of tadpole. Webbing between human fingers and toes. Plays important role in preventing cancer. © McGraw Hill LLC 3  The Cell Cycle The cell cycle is the orderly sequence of stages that occurs between the time a cell divides and the time the resulting daughter cells also divide. © McGraw Hill LLC 4  The Stages of Interphase 1 The cell cycle includes: Interphase—divided into three stages: G1—stage before DNA synthesis. S—DNA synthesis. G2—stage after DNA synthesis. Mitotic Stage. Mitosis—division of the nucleus. Cytokinesis—division of the cytoplasm. © McGraw Hill LLC 5  The Stages of Interphase 2 Figure 5.1 Access the text alternative for slide images. © McGraw Hill LLC 6  The Stages of Interphase 3 G1: cell doubles its organelles and accumulates material for DNA synthesis. G0 occurs in some cells: pause and carry out normal functions but don’t prepare to divide. S: DNA replication occurs. After DNA replication, each chromosome has gone from one DNA molecule, called a chromatid, to two DNA molecules, called sister chromatids. G2: the cell synthesizes proteins for cell division. © McGraw Hill LLC 7  The Stages of Interphase 4 Figure 5.2 Access the text alternative for slide images. © McGraw Hill LLC 8  The Mitotic Stage Mitosis, the division of the nucleus, follows interphase. The sister chromatids separate into daughter chromosomes. Distributed to two daughter nuclei. Cytokinesis, the division of the cytoplasm, follows mitosis. Two daughter cells that are identical to the mother cell are the result. © McGraw Hill LLC 9  Apoptosis Figure 5.3 Apoptosis Cell passes through typical series of events that brings about cell destruction. Caspases are the enzymes responsible. Held in check by inhibitors. Unleashed by internal or external signals. Access the text alternative for slide images. © McGraw Hill LLC (photo): Steve Gschmeissner/Science Source 10  5.2 Control of the Cell Cycle 1 Eukaryotic cells have a complex system for regulating the cell cycle. The cell cycle is controlled by. Internal signals. help control timing of events. a protein called cyclin acts as internal timekeeper for the cell. External signals tell the cell whether or not to divide. © McGraw Hill LLC 11  5.2 Control of the Cell Cycle 2 Three checkpoints control the cell cycle. G1—is DNA damaged? G2—is DNA replication complete? M—are chromosomes going to be properly distributed? Checkpoints are critical for preventing cancer development. A damaged cell should not complete mitosis. © McGraw Hill LLC 12  5.2 Control of the Cell Cycle 3 Figure 5.1 Access the text alternative for slide images. © McGraw Hill LLC 13  5.2 Control of the Cell Cycle 4 Mammalian cells enter the cell cycle only when stimulated by an external factor. Growth factors are signals that set into motion the events associated with entering the cell cycle. For example, when blood platelets release a growth factor, skin fibroblasts finish the cell cycle. © McGraw Hill LLC 14  Proto-oncogenes and Tumor Suppressor Genes 1 Two types of genes control progression through the cell cycle. Proto-oncogenes. Encode proteins that promote the cell cycle and prevent apoptosis. Likened to a gas pedal of a car. Mutate to become oncogenes (cancer-causing genes). © McGraw Hill LLC 15  Proto-oncogenes and Tumor Suppressor Genes 2 Tumor suppressor genes. Encode proteins that stop the cell cycle and promote apoptosis. Act like brakes of a car—inhibit progression through cell cycle. Mutation causes the “brakes” to not work. Gene products no longer inhibit cell cycle. © McGraw Hill LLC 16  Proto-oncogenes and Tumor Suppressor Genes 3 Figure 5.4a Access the text alternative for slide images. © McGraw Hill LLC 17  Proto-oncogenes and Tumor Suppressor Genes 4 Figure 5.4b Access the text alternative for slide images. © McGraw Hill LLC 18  Proto-oncogenes and Tumor Suppressor Genes 5 Carcinogenesis—development of cancer. Multi-stage process. Involves disruption of normal cell division and behavior. Mutation initiates cancer. Proto-oncogenes become oncogenes. Tumor suppressor genes. © McGraw Hill LLC 19  Proto-oncogenes and Tumor Suppressor Genes 6 Figure 5.5 Proto-oncogenes mutate to form oncogenes, which code for a protein that overstimulates the cell cycle. Access the text alternative for slide images. © McGraw Hill LLC 20  Proto-oncogenes and Tumor Suppressor Genes 7 Figure 5.6 Mutated tumor suppressor genes code for a protein that fails to inhibit the cell cycle. Access the text alternative for slide images. © McGraw Hill LLC 21  5.3 Mitosis: Maintaining the Chromosome Number 1 Eukaryotic chromosomes are composed of chromatin: a combination of DNA and protein, mostly histones. Dispersed and extended in a nondividing cell; DNA available for gene expression. Condensed into compact form for cell division. Histones play a role in coiling DNA tightly. © McGraw Hill LLC 22  5.3 Mitosis: Maintaining the Chromosome Number 2 Each species has a characteristic chromosome number. Diploid (2n): Cells have two (a pair) of each type of chromosome. Human body cells = 46 in 23 pairs. Haploid (1n): Cells have only one of each type of chromosome (half the diploid #). Human eggs or sperm = 23 or 1 member of each pair. © McGraw Hill LLC 23  Overview of Mitosis 1 Mitosis is division of the nuclear contents in which the chromosome number stays constant. One 2n cell becomes two 2n cells. DNA replication occurs before mitosis, producing duplicated chromosomes. © McGraw Hill LLC 24  Overview of Mitosis 2 Figure 5.7 Access the text alternative for slide images. © McGraw Hill LLC 25  Overview of Mitosis 3 After DNA replication during interphase, each chromosome is composed of two sister chromatids held together by a centromere. Sister chromatids are genetically identical. During mitosis, the centromere divides and each chromatid becomes a daughter chromosome. © McGraw Hill LLC 26  Mitosis in Detail Mitosis is nuclear division that forms two daughter nuclei with. the same number of chromosomes. the same kind of chromosomes. The spindle of microtubule fibers brings an orderly distribution of chromosomes to the daughter nuclei. Centrosomes organize spindle microtubules. Divide during late interphase. Contain centrioles in animal cells. © McGraw Hill LLC 27  Mitosis in Animal Cells 1 Prophase Nuclear membrane fragments; nucleolus begins to disappear. Centrosomes have duplicated; they begin moving to opposite poles. Chromatin condenses, and chromosomes become visible. Each composed of two sister chromatids held together at centromere. Spindle begins to form. © McGraw Hill LLC 28  Mitosis in Animal Cells 2 Prometaphase Kinetochores appear on each side of the centromere. Kinetochore of each chromatid is attached to a kinetochore spindle fiber. Spindle fibers extend from the poles to the chromosomes. Kinetochore fibers pull chromosomes back and forth toward alternate poles to begin aligning chromosomes. © McGraw Hill LLC 29  Mitosis in Animal Cells 3 Figure 5.8 left Access the text alternative for slide images. (photos) (animal early prophase, prophase, metaphase, anaphase, telophase): Ed Reschke; (animal prometaphase): Michael Abbey/Science Source; (plant early prophase, plant prometaphase): Ed Reschke; (plant prophase, metaphase, anaphase, telophase): Kent Wood/Science Source © McGraw Hill LLC 30  Mitosis in Animal Cells 4 Metaphase Spindle is fully formed and consists of poles, asters, and fibers. Polar fibers overlap. Centromeres of chromosomes are aligned at the metaphase plate. Anaphase Centromeres divide, and sister chromatids are moved to opposite poles by fibers. Kinetochore spindle fibers shorten, pulling daughter chromosomes. Polar spindle fibers push the poles apart. © McGraw Hill LLC 31  Mitosis in Animal Cells 5 Telophase Spindle disappears. Nuclear membrane components reassemble around daughter chromosomes. Chromosomes become more diffuse again. Nucleolus appears in each daughter nucleus. Cytokinesis begins. © McGraw Hill LLC 32  Mitosis in Animal Cells 6 Figure 5.8 right Access the text alternative for slide images. (photos) (animal early prophase, prophase, metaphase, anaphase, telophase): Ed Reschke; (animal prometaphase): Michael Abbey/Science Source; (plant early prophase, plant prometaphase): Ed Reschke; (plant prophase, metaphase, anaphase, telophase): Kent Wood/Science Source © McGraw Hill LLC 33  Mitosis in Plant Cells 1 Permits growth and repair as in animal cells. Occurs in meristematic tissues that divide throughout life of plant. Goes through same phases as animal cells. Does not use centrioles or asters. © McGraw Hill LLC 34  Mitosis in Plant Cells 2 Figure 5.8 left Access the text alternative for slide images. (photos) (animal early prophase, prophase, metaphase, anaphase, telophase): Ed Reschke; (animal prometaphase): Michael Abbey/Science Source; (plant early prophase, plant prometaphase): Ed Reschke; (plant prophase, metaphase, anaphase, telophase): Kent Wood/Science Source © McGraw Hill LLC 35  Mitosis in Plant Cells 3 Figure 5.8 right Access the text alternative for slide images. (photos) (animal early prophase, prophase, metaphase, anaphase, telophase): Ed Reschke; (animal prometaphase): Michael Abbey/Science Source; (plant early prophase, plant prometaphase): Ed Reschke; (plant prophase, metaphase, anaphase, telophase): Kent Wood/Science Source © McGraw Hill LLC 36  Cytokinesis in Animal and Plant Cells 1 Cytokinesis in animal cells. Cleavage furrow forms between daughter nuclei. Contractile ring of actin filaments constricts, deepening the furrow. Process continues until separation is complete. © McGraw Hill LLC 37  Cytokinesis in Animal and Plant Cells 2 Figure 5.9 Access the text alternative for slide images. © McGraw Hill LLC (photos) (top): National Institutes of Health (NIH)/USHHS; (bottom): Steve Gschmeissner/SPL/Brand X Pictures/Getty Images 38  Cytokinesis in Animal and Plant Cells 3 Cytokinesis in plant cells. Requires creation of new cell wall between daughter cells. A flattened, small disk appears between daughter cells. Vesicles move to the disk and fuse. A cell plate forms. Vesicle membranes complete plasma membranes for new cells and release molecules to form new cell walls. © McGraw Hill LLC 39  Cytokinesis in Animal and Plant Cells 4 Figure 5.10 © McGraw Hill LLC Biophoto Associates/Science Source 40  5.4 Meiosis: Reducing the Chromosome Number Meiosis Occurs in the life cycle of sexually reproducing organisms. Reduces the chromosome number in half. Provides offspring with a different combination of traits from that of either parent. © McGraw Hill LLC 41  Overview of Meiosis Begins with one diploid parental cell. Requires two cell divisions. Ends with four haploid daughter cells. One chromosome of each homologous pair inherited from one parent, the other inherited from the other parent. © McGraw Hill LLC 42  Meiosis I Homologues line up, side by side, in a process called synapsis. Pairs of homologous chromosomes align on metaphase plate. When homologous pairs separate, each daughter cell receives one member of the pair. The cells are now haploid. © McGraw Hill LLC 43  Meiosis II and Fertilization 1 No replication of DNA occurs between meiosis I and meiosis II. Centromeres divide and sister chromatids migrate to opposite poles to become individual chromosomes. Each of the four daughter cells produced has the haploid chromosome number. Each chromosome is composed of one chromatid. © McGraw Hill LLC 44  Meiosis II and Fertilization 2 Figure 5.11 Access the text alternative for slide images. © McGraw Hill LLC 45  Meiosis II and Fertilization 3 Fertilization Daughter cells of meiosis mature into gametes. Sperm and eggs (also called sex cells). Gametes fuse during the process called fertilization. Restores diploid number: (n) + (n) = (2n). Creates a cell that will develop into a new individual. © McGraw Hill LLC 46  Meiosis in Detail Meiosis requires two nuclear divisions. Meiosis results in four daughter nuclei. Each daughter nucleus has half of the chromosomes as the parent cell. © McGraw Hill LLC 47  First Division 1 Meiosis I is divided into. Prophase I. Anaphase I. Metaphase I. Telophase I. Meiosis helps ensure genetic variation. Genetic variation occurs in two ways: Crossing-over. Independent assortment. © McGraw Hill LLC 48  First Division 2 Figure 5.12 Access the text alternative for slide images. © McGraw Hill LLC 49  First Division 3 Figure 5.12 top Access the text alternative for slide images. © McGraw Hill LLC 50  First Division 4 Figure 5.12 bottom Access the text alternative for slide images. © McGraw Hill LLC 51  Prophase I Spindle appears, nuclear envelope fragments, and nucleolus disappears. Homologues pair up during synapsis. Crossing-over occurs: the exchange of genetic material between nonsister chromatids of homologues. After crossing-over, the two chromatids of a chromosome are different. One has the original genetic material. One has recombined genetic material. © McGraw Hill LLC 52  Crossing-Over During Prophase I Figure 5.13 Access the text alternative for slide images. © McGraw Hill LLC 53  Metaphase I and Anaphase I 1 Metaphase I Homologous chromosome pairs line up at metaphase plate such that maternal or paternal member may be oriented toward either pole. Anaphase I Independent assortment occurs when these homologues separate and are pulled to opposite poles by spindle fibers during anaphase I. © McGraw Hill LLC 54  Metaphase I and Anaphase I 2 Independent assortment generates cells with different combinations of maternal and paternal chromosomes. In humans, with 23 pairs of chromosomes, the number of possible combinations is 223 , or 8,388,608. This value does not include genetic recombination due to crossing-over. © McGraw Hill LLC 55  Independent Assortment During Meiosis I Figure 5.14 Two possible orientations of chromosome pairs at the metaphase plate are shown. Access the text alternative for slide images. © McGraw Hill LLC 56  Telophase I Depending on the species, it may or may not occur at end of meiosis I. Nuclear envelopes re-form. Nucleoli reappear. Cytokinesis may occur, producing two daughter cells which are haploid. Daughter cells have one chromosome from each homologous pair. © McGraw Hill LLC 57  Interkinesis Figure 5.12 last panel Interkinesis is the period of time between meiosis I and meiosis II. No replication of DNA. Access the text alternative for slide images. © McGraw Hill LLC 58  Second Division 1 Phases of Meiosis II Prophase II. Cells have one chromosome from each homologous pair. A spindle appears. The nuclear envelope disassembles, and the nucleolus disappears. Each duplicated chromatid attaches to the spindle. Metaphase II. Chromosomes consisting of pairs of sister chromatids line up at the metaphase plate. © McGraw Hill LLC 59  Second Division 2 Phases of Meiosis II Anaphase II. Sister chromatids separate and become daughter chromosomes that migrate toward the poles. Telophase II. The spindle disappears. The nuclear envelope re-forms. Cytokinesis occurs to produce four haploid daughter cells. © McGraw Hill LLC 60  Second Division 3 Figure 5.15 Access the text alternative for slide images. © McGraw Hill LLC 61  Second Division 4 Figure 5.15 top Access the text alternative for slide images. © McGraw Hill LLC 62  Second Division 5 Figure 5.15 bottom Access the text alternative for slide images. © McGraw Hill LLC 63  The Importance of Meiosis 1 Meiosis produces haploid cells from diploid cells. Genetic variation produces cells no longer identical to parental cell. Genetic variation occurs in two ways: First, crossing between nonsister chromatids. Second, the independent assortment of chromosomes during anaphase I. © McGraw Hill LLC 64  The Importance of Meiosis 2 Upon fertilization, combining of chromosomes from genetically different gametes helps ensure offspring are not identical to parents. This genetic variability is the main advantage of sexual reproduction. Long-term, genetic variation increases the survival of a species. © McGraw Hill LLC 65  5.5 Comparison of Meiosis With Mitosis 1 DNA replication occurs only once prior to either meiosis or mitosis. Meiosis requires two nuclear divisions, mitosis requires one. Meiosis produces four daughter cells, mitosis produces two. © McGraw Hill LLC 66  5.5 Comparison of Meiosis With Mitosis 2 Four daughter cells from meiosis are haploid; two from mitosis are diploid. Daughter cells from meiosis are genetically variable, while those from mitosis are genetically identical. © McGraw Hill LLC 67  Meiosis versus Mitosis 1 Figure 5.16 Access the text alternative for slide images. © McGraw Hill LLC 68  Meiosis versus Mitosis 2 Figure 5.16 top Access the text alternative for slide images. © McGraw Hill LLC 69  Meiosis versus Mitosis 3 Figure 5.16 bottom Access the text alternative for slide images. © McGraw Hill LLC 70  Occurrence Meiosis occurs only at certain times of the life cycle of sexually reproducing organisms. After the reproductive organs mature to produce gametes. Mitosis takes place almost continuously in all tissues as part of growth and repair. © McGraw Hill LLC 71  Comparison of Meiosis I to Mitosis 1 Homologous chromosomes pair and cross-over during prophase I of meiosis I, but not during mitosis. Paired homologous chromosomes align at the metaphase plate during metaphase I; individual chromosomes align at metaphase plate in mitosis. Homologous chromosomes separate and move to opposite poles during anaphase I; centromeres split, and sister chromatids move to opposite poles in anaphase of mitosis. © McGraw Hill LLC 72  Comparison of Meiosis I to Mitosis 2 TABLE 5.1 Comparison of Meiosis I with Mitosis. Meiosis I Mitosis Prophase I Prophase Pairing of homologous No pairing of chromosomes. chromosomes. Metaphase I Metaphase Homologous duplicated Duplicated chromosomes at chromosomes at metaphase plate. metaphase plate. Anaphase I Anaphase Homologous chromosomes Sister chromatids separate, separate. becoming daughter chromosomes that move to the poles. Telophase I Telophase/Cytokinesi Two haploid daughter cells. Two diploid daughter cells, identical to the parental cell. © McGraw Hill LLC 73  Comparison of Meiosis I to Mitosis 3 TABLE 5.2 Comparison of Meiosis II with Mitosis. Meiosis II Mitosis Prophase II Prophase No pairing of chromosomes. No pairing of chromosomes. Metaphase II Metaphase Haploid number of duplicated Duplicated chromosomes at chromosomes at metaphase plate. metaphase plate. Anaphase II Anaphase Sister chromatids separate, Sister chromatids separate, becoming daughter chromosomes becoming daughter chromosomes that move to the poles. that move to the poles. Telophase II Telophase/Cytokinesi Four haploid daughter cells, not Two diploid daughter cells, identical to parental cell. identical to the parental cell. © McGraw Hill LLC 74  5.6 The Human Life Cycle Both mitosis and meiosis are required. At fertilization, a haploid (n) sperm and a haploid (n) egg fuse. The resulting zygote has a diploid (2n) number of chromosomes. The fetus divides by mitosis for growth and development. After birth, mitosis allows continued growth and tissue repair. © McGraw Hill LLC 75  Spermatogenesis and Oogenesis in Humans Meiosis in the testes of males is called spermatogenesis. Produces sperm. Meiosis in the ovaries of females is called oogenesis. Produces eggs. © McGraw Hill LLC 76  Life Cycle of Humans Figure 5.17 Access the text alternative for slide images. © McGraw Hill LLC 77  Spermatogenesis 1 Spermatogenesis occurs in testes of human males. The process begins at puberty and continues throughout life. Primary spermatocytes (2n) divide in meiosis I to form two secondary spermatocytes (1n). Secondary spermatocytes divide in meiosis II to produce four spermatids (1n). Spermatids then mature to sperm (spermatozoa). © McGraw Hill LLC 78  Spermatogenesis 2 Figure 5.18 © McGraw Hill LLC 79  Oogenesis 1 Oogenesis begins in the ovaries of a female fetus. All primary oocytes are arrested in prophase I. Resumes at puberty. One primary oocyte continues the process of meiosis during each menstrual cycle. Primary oocyte (2n) divides in meiosis I to produce one secondary oocyte (1n) and one polar body (1n). Division is unequal as secondary oocyte receives most of the cell contents and half the chromosomes. © McGraw Hill LLC 80  Oogenesis 2 If the secondary oocyte (1n) is fertilized, meiosis II will proceed. Another unequal division will occur, with the egg (1n) receiving most of the cytoplasm. A second polar body is also formed. If the secondary oocyte is not fertilized, it disintegrates. © McGraw Hill LLC 81  Oogenesis 3 Figure 5.19 Access the text alternative for slide images. © McGraw Hill LLC 82  Oogenesis 4 Figures 5.18 and 5.19 Access the text alternative for slide images. © McGraw Hill LLC 83  End of Main Content Because learning changes everything. ® www.mheducation.com © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.