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Chromosomes and Cellular Reproduction
Benjamin A. Pierce GENETICS A Conceptual Approach FIFTH EDITION CHAPTER 2 Chromosomes and Cellular Reproduction © 2014 W. H. Freeman and Company
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Replace with photo from page 17, first page of Chapter 2
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Chromosomes and Cellular Reproduction
Prokaryote and Eukaryote Cell Reproduction Sexual Reproduction
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Prokaryote vs. Eukaryote
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Prokaryote vs. Eukaryote
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Prokaryote Unicellular, no membrane bound organelles.
Prokaryotic DNA does not exist in the highly ordered and packed arrangement. Made up of eubacteria and archaea.
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Eukaryote Both unicellular and multicellular with membrane-bound organelles. Genetic material is surrounded in a nuclear envelope to form a nucleus. DNA is closely associated with histones to form tightly packed chromosomes.
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Viruses Neither prokaryotic nor eukaryotic
Outer protein coat surrounding nucleic acid
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Prokaryotic Cell Reproduction
Simple division: separation of replicated circular chromosome Origin of replication High rate of replication
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Eukaryotic Cell Replication
Eukaryotic chromosomes: Homologous pair Chromosome structure The cell cycle Genetic consequences of the cell cycle
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Homologous Pair Diploid cells carry two sets of genetic information.
Haploid cells carry one set of genetic information.
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Figure 2. 6. Diploid eukaryotic cells have two sets of chromosomes
Figure 2.6. Diploid eukaryotic cells have two sets of chromosomes. (a) A set of chromosomes from a female human cell. Each pair of chromosomes is hybridized to a uniquely colored probe, giving it a distinct color. (b) The chromosomes are present in homologous pairs, which consist of chromosomes that are alike in size and structure and carry information for the same characteristics. [Part a: Courtesy of Dr. Thomas Ried and Dr. Evelin Schrock.]
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Figure 2. 6. Diploid eukaryotic cells have two sets of chromosomes
Figure 2.6. Diploid eukaryotic cells have two sets of chromosomes. (a) A set of chromosomes from a female human cell. Each pair of chromosomes is hybridized to a uniquely colored probe, giving it a distinct color. (b) The chromosomes are present in homologous pairs, which consist of chromosomes that are alike in size and structure and carry information for the same characteristics. [Part a: Courtesy of Dr. Thomas Ried and Dr. Evelin Schrock.]
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Concept Check 1 Diploid cells have: a. Two chromosomes b. Two sets of chromosomes c. One set of chromosomes d. Two pairs of homologous chromosomes
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Chromosome Structure Centromere: attachment point for spindle microtubules Telomeres: tips of a linear chromosome Origins of replication: where the DNA synthesis begins
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Figure 2.7 Each eukaryotic chromosome has a centromere and telomeres.
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The Cell Cycle Life cycle of the cell
Interphase: an extended period between cell divisions, DNA synthesis, and chromosome replication phase M phase: mitotic phase Phase check points: key transition points
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Figure 2.9 The cell cycle consists of interphase and M phase.
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Interphase G1, S, G2 G1: Growth; proteins necessary for cell division synthesized G1/S checkpoint: regulated decision point S: DNA synthesis G2: biochemical preparation for cell division G2/M checkpoint: only passed if DNA completely replicated and undamaged
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M Phase Mitosis: separation of sister chromatids
Cytokinesis: separation of cytoplasm
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Mitosis Prophase Prometaphase Metaphase Anaphase Telophase
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Figure 2. 10 The cell cycle is divided into stages
Figure 2.10 The cell cycle is divided into stages. [Photographs by Conly L. Rieder/Biological Photo Service.]
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Figure 2. 10 The cell cycle is divided into stages
Figure 2.10 The cell cycle is divided into stages. [Photographs by Conly L. Rieder/Biological Photo Service.]
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Figure 2. 10 The cell cycle is divided into stages
Figure 2.10 The cell cycle is divided into stages. [Photographs by Conly L. Rieder/Biological Photo Service.]
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Figure 2. 10 The cell cycle is divided into stages
Figure 2.10 The cell cycle is divided into stages. [Photographs by Conly L. Rieder/Biological Photo Service.]
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Figure 2. 10 The cell cycle is divided into stages
Figure 2.10 The cell cycle is divided into stages. [Photographs by Conly L. Rieder/Biological Photo Service.]
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Figure 2. 10 The cell cycle is divided into stages
Figure 2.10 The cell cycle is divided into stages. [Photographs by Conly L. Rieder/Biological Photo Service.]
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Genetic Consequences of the Cell Cycle
Producing two cells that are genetically identical to each other and with the cell that gave rise to them. Newly formed cells contain a full complement of chromosomes. Each newly formed cell contains approximately half the cytoplasm and organelle content of the original parental cell.
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Concept Check 2 Which is the correct order of stages in the cell cycle? G1, S, prophase, metaphase, anaphase S, G1, prophase, metaphase, anaphase prophase, S, G1, metaphase, anaphase S, G1, anaphase, prophase, metaphase
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Concept Check 2 Which is the correct order of stages in the cell cycle? G1, S, prophase, metaphase, anaphase S, G1, prophase, metaphase, anaphase prophase, S, G1, metaphase, anaphase S, G1, anaphase, prophase, metaphase
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Sexual Reproduction and Genetic Variation
Meiosis: the production of haploid gametes Fertilization: the fusion of haploid gametes Genetic variation: consequences of meiosis
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Meiosis Interphase: DNA synthesis and chromosome replication phase
Meiosis I: separation of homologous chromosome pairs, and reduction of the chromosome number by half Meiosis II: separation of sister chromatids, also known as equational division
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Figure 2.13. Meiosis includes two cell divisions.
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Meiosis I Prophase I Synapsis: close pairing of homologous chromosome
Tetrad: closely associated four-sister chromatids of two homologous chromosomes Crossing over: crossing over of chromosome segments from the sister chromatid of one chromosome to the sister chromatid of the other synapsed chromsome―exchange of genetic information, the first mechanism of generating genetic variation in newly formed gametes
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Figure 2.13. Meiosis includes two cell divisions.
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Meiosis I Metaphase I: random alignment of homologous pairs of chromosomes along the metaphase plate Anaphase I: separation of homologous chromosome pairs, and the random distribution of chromosomes into two newly divided cells―second mechanism of generating genetics variation in the newly formed gametes Telophase I Interkinesis
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Meiosis II Prophase II Metaphase II Anaphase II Telophase II
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Fig 2.15: Meiosis is divided into stages.
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Consequences of Meiosis and Genetic Variation
Four cells are produced from each original cell. Chromosome number in each new cell is reduced by half. The new cells are haploid. Newly formed cells from meiosis are genetically different from one another and from the parental cell.
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Figure 2.16 Crossing over produces genetic variation.
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Figure 2.17 Genetic variation is produced through the random distribution of chromosomes in meiosis.
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Concept Check 3 Which of the following events takes place in meiosis II, but not in meiosis I? crossing over contraction of chromosomes separation of homologous chromosomes separation of chromatids
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Concept Check 3 Which of the following events takes place in meiosis II, but not in meiosis I? crossing over contraction of chromosomes separation of homologous chromosomes separation of chromatids
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Figure 2.18: Mitosis and meiosis compared.
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The Separation of Sister Chromatids and Homologous Chromosomes
Cohesin: a protein that holds the chromatids together and is key to the behavior of chromosomes in mitosis and meiosis
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Figure Cohesin controls the separation of chromatids and chromosomes in (a) mitosis and (b) meiosis.
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Meiosis in the Life Cycle of Animals and Plants
Meiosis in animals Spermatogenesis: male gamete production Oogenesis: female gamete production Meiosis in plants
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Figure 2.20 Gamete formation in animals.
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Figure 2.21 Plants alternate between diploid and haploid life stages.
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Figure 2.22: Sexual reproduction in flowering plants.
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