Chapters 9-10 Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Learning Objectives 1. 2. 3. 4. 5. 6. Define Genetics? Genome? Chromosomes? Genes? Karyotype? The importance of Mitosis The importance of Meiosis What are the differences between Mitosis and Meiosis? The cytokinesis in plants and bacteria Meiosis and gender outcome Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Genetics Genetics = the study of heredity Genes = contain instructions for protein production Genome = complete collection of an organism’s genetic information Genome found in DeoxyriboNucleic Acid DNA = molecule of heredity DNA + protein complex = Chromosomes Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr DNA Chromosomes When DNA is wrapped around proteins, it forms chromatin Chromatin is packaged in units called chromosomes Figure 9.6 : Chromosomes and DNA Replication Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Karyotype Karyotype= arrangement of a full set of chromosomes according to their size and function Humans = 46 chromosomes 23 pairs 22 matched pairs = autosomes 1 pair = sex chromosomes female matched XX male unmatched XY Figure 9.7 : A karyotype displays a full set of chromosomes Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Cell division Mitosis sentientbridge555.com Division of somatic (non sex) cells Produces identical cells Conservation of the number of chromosomes Functions: Growth Repair Replacement Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr www.rubberboas.com Cell division Meiosis Division of gamete (sex) cells (sperm cell, egg cell) Produces 4 genetically different cells Reduction of the number of chromosomes by half Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr The Cell Cycle 2 main phases: Interphase = the cell carries out its work, chromosomes are duplicated in preparation for cell division (24 hrs) Mitotic phase = mitosis and cytokinesis (30 min) Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Figure 9.9 : The Cell Cycle Interphase Interphase = 3 phases G1 = Gap-one The cell is growing and carrying out its normal functions (12 hrs) S = Synthesis The cell is replicating its DNA in preparation for Mitotic phase (6 hrs) G2 = Gap-two The cell continues its normal functions (6 hrs) Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Figure 9.9 : The Cell Cycle Interphase Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Mitotic Phase Mitotic phase = 2 phases Mitosis separation of a cell’s duplicated chromosomes Cytokinesis physical separation of one cell into two daughter cells Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Figure 9.9 : The Cell Cycle Prophase Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Metaphase Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Anaphase Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Telophase Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Cytokinesis Cytokinesis Animal cells Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Cytokinesis Cytokinesis Plant cells 1. Membrane-like vesicles, containing precursors to the cell wall, accumulate near the metaphase plate. 2. Vesicles fuse together, forming a cell plate that grows toward the parent cell wall Figure 9.12 : Cytokinesis in Plants Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr 3. Newly fromed plasma membrane and cell wall fuse with parent membrane and wall, forming 2 distinct daughter cells Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Mitotic Phase Prophase Centrosomes migration toward opposite ends Nuclear envelope breaks up Metaphase Chromosomes are arranged at the level of the equatorial plane Anaphase Sister chromatids are pulled apart by shortening of microtubules Telophase Nuclear envelope reforms Cytokinesis Cell divides Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Binary Fission Bacteria Figure 9.13 : Binary Fission in Bacteria Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Passing on Genetic Information Half of each person’s genome comes from the father, and half from the mother. Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Meiosis Human somatic cells = diploid = paired sets of chromosomes Gametes = reproductive cells = haploid = single set of chromosomes Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr 23 chromosomes from father + 23 chromosomes from mother = 46 chromosomes Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Mitosis vs Meiosis Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr (a) Meiosis I Meiosis II Haploid Diploid cytokinesis cytokinesis End of interphase Prophase I DNA has already duplicated Metaphase I Homologous chromosomes link as they condense, forming tetrads. Microtubules move homologous chromosomes to metaphase plate. Crossing over occurs. Independent assortment occurs. Anaphase I Microtubules separate homologous chromosomes (sister chromatids remain together). Telophase I Prophase II Two haploid daughter cells result from cytokinesis. (Brief) Metaphase II Sister chromatids line up at new metaphase plate. Anaphase II Sister chromatids separate. Telophase II Four haploid cells result. Compare these cells to the cells above Telophase II First important source of genetic variation Second important source of genetic variation (b) Crossing over (c) Independent assortment Exchange of parts of non-sister chromatids. Random alignment of maternal/paternal chromosomes at the metaphase plate. duplicated duplicated maternal paternal chromosome chromosome Metaphase I Metaphase I tetrad sister chromatids non-sister chromatids Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr In the sequence above, homologous chromosomes lined up this way in Metaphase I . . . ... but they could have lined up this way, yielding a different outcome. Metaphase II Prophase I Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Metaphase I Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Meiosis 2 stages BUT only one interphase: one duplication of DNA Meiosis I Prophase I Metaphase I Anaphase I Telophase I Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Meiosis II Prophase II Metaphase II Anaphase II Telophase II Meiosis I Prophase I Nuclear envelope breaks up Crossing over: 2 pairs of homologous chromosomes exchange genes Metaphase I Homologous chromosomes line up at the level of the equatorial plane Independent assortment Anaphase I Homologous chromosomes separate Telophase I Nuclear envelope reforms Cytokinesis I Cell divides Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Meiosis II Prophase II Nuclear envelope breaks up Metaphase II Chromatids line up at the level of the equatorial plane Anaphase II Sister chromatids separate and are pulled to opposite poles Telophase II Nuclear envelope reforms Cytokinesis II 4 new cells are formed Only half of the number of chromosomes as the parent cell Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr What is the significance of meiosis? 1. Meiosis generates genetic diversity every person is unique Through crossing over or recombination Crossing over = a process in which homologous chromosomes exchange reciprocal portions of themselves Prophase I Through independent assortments Random distribution of homologous chromosome pairs during meiosis Metaphase I 2. Meiosis determines the sex outcome Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Meiosis and gender outcome Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Reproduction Not all reproduction is sexual reproduction Union of 2 reproductive cells to create a new organism Ex. Human reproduction Most types of organisms are capable of asexual reproduction (exception mammals and birds) Asexual reproduction No reproductive cells No mixing and matching of chromosomes Several forms Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Reproduction Asexual reproduction Ex. Binary fission in bacteria Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Reproduction Asexual reproduction Ex. Vegetative reproduction a « cutting » taken from a plant and planted correctly Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr Reproduction Asexual reproduction Ex. Regeneration (sea star, lizards…) Copyright © 2005 Pearson Prentice Hall, Inc. Dr Joelle Nader-Nasr
