Lecture Slides: Genetics - Chapter 2 - Chromosomes and Cellular Reproduction - PDF

Benjamin A. Pierce Genetic s A Conceptual Approach SEVENTH EDITION Lecture Slides CHAPTER 2 Chromosomes and Cellular Reproduction Copyright © 2020, W.H. Freeman and Company Chromosomes and Cellu...

Benjamin A. Pierce Genetic s A Conceptual Approach SEVENTH EDITION Lecture Slides CHAPTER 2 Chromosomes and Cellular Reproduction Copyright © 2020, W.H. Freeman and Company Chromosomes and Cellular Reproduction (1 of 2)  Chromosomes and Cellular Reproduction (2 of 2) Prokaryote and Eukaryote Cell Reproduction Sexual Reproduction Prokaryote vs. Eukaryote (1 of 2) Prokaryote vs. Eukaryote (2 of 2)  Prokaryote Unicellular, no membrane-bound organelles. Prokaryotic DNA does not exist in the highly ordered and packed arrangement. Made up of eubacteria and archaea.  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.  Concept Check 1 (1 of 2) List several characteristics that bacteria and archaea have in common and that distinguish them from eukaryotes.  Concept Check 1 (2 of 2) List several characteristics that bacteria and archaea have in common and that distinguish them from eukaryotes. Bacteria and archaea are prokaryotes. They differ from eukaryotes: – no nucleus – a single circular chromosomal genome (usually) – a smaller amount of DNA  Viruses Neither prokaryotic nor eukaryotic Outer protein coat surrounding nucleic acid  Prokaryotic Cell Reproduction Simple division: separation of replicated circular chromosome Origin of replication High rate of replication  Eukaryotic Cell Replication Eukaryotic chromosomes – Homologous pairs – Chromosome structure – Cell cycle – Genetic consequences of the cell cycle  Homologous Pairs (1 of 2) Diploid cells carry two sets of genetic information. Haploid cells carry one set of genetic information. Homologous Pairs (2 of 2)  Concept Check 2 (1 of 2) Diploid cells have a. two chromosomes. b. two sets of chromosomes. c. one set of chromosomes. d. two pairs of homologous chromosomes.  Concept Check 2 (2 of 2) Diploid cells have a. two chromosomes. b. two sets of chromosomes. c. one set of chromosomes. d. two pairs of homologous chromosomes.  Chromosome Structure (1 of 3) Centromere: attachment point for spindle microtubules Telomeres: tips of a linear chromosome Origins of replication: where the DNA synthesis begins Chromosome Structure (2 of 3) Chromosome Structure (3 of 3)  Concept Check 3 (1 of 2) What would be the result if a chromosome did not have a kinetochore?  Concept Check 3 (2 of 2) What would be the result if a chromosome did not have a kinetochore? No kinetochore: – Spindle microtubules would not attach to the chromosome. – The chromosome would not be drawn into a newly formed nucleus. – The resulting daughter cells would be missing a chromosome.  The Cell Cycle (1 of 2) Life cycle of the cell Interphase: an extended period between cell divisions, DNA synthesis, and chromosome replication phase M phase: mitotic phase Phase checkpoints: key transition points The Cell Cycle (2 of 2)  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 is completely replicated and undamaged  M Phase Mitosis: separation of sister chromatids Cytokinesis: separation of cytoplasm  Mitosis (1 of 3) Prophase Prometaphase Metaphase Anaphase Telophase Mitosis (2 of 3) Mitosis (3 of 3)  TABLE 2.1 Features of the cell cycle Stage Major Features G0 phase Stable, nondividing period of variable length. Interphase G1 phase Growth and development of the cell; G 1/S checkpoint. S phase Synthesis of DNA G2 phase Preparation for division; G2 /M checkpoint. M phase Prophase Chromosomes condense and mitotic spindle forms. Prometaphase Nuclear envelope disintegrates, and spindle microtubules anchor to kinetochores. Metaphase Chromosomes align on the metaphase plate; spindle-assembly checkpoint. Anaphase Sister chromatids separate, becoming individual chromosomes that migrate toward spindle poles. Telophase Chromosomes arrive at spindle poles, the nuclear envelope re-forms, and the condensed chromosomes relax. Cytokinesis Cytoplasm divides; cell wall forms in plant cells.  Concept Check 4 (1 of 2) Which is the correct order of stages in the cell cycle? a. G1, S, prophase, metaphase, anaphase b. S, G1, prophase, metaphase, anaphase c. prophase, S, G1, metaphase, anaphase d. S, G1, anaphase, prophase, metaphase  Concept Check 4 (2 of 2) Which is the correct order of stages in the cell cycle? a. G1, S, prophase, metaphase, anaphase b. S, G1, prophase, metaphase, anaphase c. prophase, S, G1, metaphase, anaphase d. S, G1, anaphase, prophase, metaphase  Genetic Consequences of the Cell Cycle (1 of 2) Cycle produces 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. Genetic Consequences of the Cell Cycle (2 of 2)  Sexual Reproduction and Genetic Variation Meiosis: the production of haploid gametes Fertilization: the fusion of haploid gametes Genetic variation: consequences of meiosis  Meiosis (1 of 2) 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 Meiosis (2 of 2)  Meiosis I (1 of 3) Prophase I – Synapsis: close pairing of homologous chromosomes – 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 chromosome―exchange of genetic information, the first mechanism of generating genetic variation in newly formed gametes Meiosis I (2 of 3)  Meiosis I (3 of 3) 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 genetic variation in the newly formed gametes Telophase I Interkinesis  Meiosis II (1 of 2) Prophase II Metaphase II Anaphase II Telophase II Meiosis II (2 of 2)  TABLE 2.2 Major events in each stage of meiosis Stage Major Features Meiosis I Prophase I Chromosomes condense, homologous chromosomes synapse, crossing over takes place, the nuclear envelope breaks down, and the mitotic spindle forms. Metaphase I Homologous pairs of chromosomes line up on the metaphase plate. Anaphase I The two chromosomes (each with two chromatids) of a homologous pair separate and move toward opposite poles. Telophase I Chromosomes arrive at the spindle poles. Cytokinesis The cytoplasm divides to produce two cells, each having half the original number of chromosomes. Interkinesis In some types of cells, the spindle breaks down, chromosomes relax, and a nuclear envelope re-forms, but no DNA synthesis takes place. Meiosis II Prophase II* Chromosomes condense, the spindle forms, and the nuclear envelope disintegrates. Metaphase II Individual chromosomes line up on the metaphase plate. Anaphase II Sister chromatids separate and move as individual chromosomes toward the spindle poles. Telophase II Chromosomes arrive at the spindle poles; the spindle breaks down and a nuclear envelope re-forms. Cytokinesis The cytoplasm divides. *Only in cells in which the spindle has broken down, chromosomes have relaxed, and the nuclear envelope has re- formed in telophase I. Other types of cells proceed directly to metaphase II after cytokinesis.  Concept Check 5 (1 of 2) Which event takes place in meiosis II but not in meiosis I? a. crossing over b. contraction of chromosomes c. separation of homologous chromosomes d. separation of chromatids  Concept Check 5 (2 of 2) Which event takes place in meiosis II but not in meiosis I? a. crossing over b. contraction of chromosomes c. separation of homologous chromosomes d. separation of chromatids Consequences of Meiosis and Genetic Variation (1 of 4) 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. Consequences of Meiosis and Genetic Variation (2 of 4) Consequences of Meiosis and Genetic Variation (3 of 4) Consequences of Meiosis and Genetic Variation (4 of 4)  TABLE 2.3 Comparison of mitosis, meiosis I, and meiosis II Event Mitosis Meiosis I Meiosis II Cell division Yes Yes Yes Reduction in chromosome No Yes No number Genetic variation produced No Yes No Crossing over No Yes No Random distribution of maternal No Yes No and paternal chromosomes Metaphase Individual Homologous pairs line up Individual chromosomes line up chromosomes line up Anaphase Chromatids separate Homologous Chromatids separate chromosomes separate  The Separation of Sister Chromatids and Homologous Chromosomes (1 of 2) Cohesin: a protein that holds the chromatids together and is key to the behavior of chromosomes in mitosis and meiosis The Separation of Sister Chromatids and Homologous Chromosomes (2 of 2)  Concept Check 6 (1 of 2) How does shugoshin affect sister chromatids in meiosis I and meiosis II?  Concept Check 6 (2 of 2) How does shugoshin affect sister chromatids in meiosis I and meiosis II? During anaphase I: – Shugoshin protects cohesin at the centromeres from the action of separase.  Centromeric cohesin remains intact.  The sister chromatids remain togethe During Anaphase II: – Shugoshin breaks down.  Centromeric cohesin is cleaved by separase.  The sister chromatids separate.  Meiosis in the Life Cycle of Animals and Plants (1 of 2) Meiosis in animals – Spermatogenesis: male gamete production – Oogenesis: female gamete production Meiosis in plants Meiosis in the Life Cycle of Animals and Plants (2 of 2)  Concept Check 7 (1 of 2) A secondary spermatocyte has 12 chromosomes. How many chromosomes will be found in the primary spermatocyte that gave rise to it? a. 6 b. 12 c. 18 d. 24  Concept Check 7 (2 of 2) A secondary spermatocyte has 12 chromosomes. How many chromosomes will be found in the primary spermatocyte that gave rise to it? a. 6 b. 12 c. 18 d. 24 Concept Check 8 (1 of 4) Concept Check 8 (2 of 4)  Concept Check 8 (3 of 4) Which structure is diploid? a. microspore b. egg c. megaspore d. microsporocyte  Concept Check 8 (4 of 4) Which structure is diploid? a. microspore b. egg c. megaspore d. microsporocyte