Copyright © 2009 Pearson Education, Inc. PowerPoint ® Lecture Presentation for Concepts of Genetics Ninth Edition Klug, Cummings, Spencer, Palladino Chapter 2 Mitosis and Meiosis Lectures by David Kass with contributions from John C. Osterman. Copyright © 2009 Pearson Education, Inc.
What is the difference between prokaryotic and eukaryotic organisms?
Copyright © 2009 Pearson Education, Inc. Organisms organize DNA in structures called chromosomes
Copyright © 2009 Pearson Education, Inc. Chromatin/Chromosomes ChromatinChromosomes
Copyright © 2009 Pearson Education, Inc. Cell Division Prokaryotes Binary fission Eukaryotes transmission of genetic material from one generation of cells to next involves: Mitosis Meiosis
Copyright © 2009 Pearson Education, Inc. Figure 2.1
Copyright © 2009 Pearson Education, Inc. Figure 2.2 E. coli – Binary Fission
Copyright © 2009 Pearson Education, Inc. Section 2.2 – Homologous Chromosomes In each homologous pair of chromosomes, one member is derived from each parent. Standford.edu Identify location of: Sister chromatids Centromere Telomeres
Copyright © 2009 Pearson Education, Inc. Figure 2.3
Copyright © 2009 Pearson Education, Inc. Diploid vs Haploid Organisms Diploid Organisms 2 copies of each chromosome for most of its life cycle Haploid Organisms 1 copy of each chromosome for most of its life cycle Ex. Bacteria, yeasts and molds, some plants such as bryophytes (mosses)
Copyright © 2009 Pearson Education, Inc. Figure 2.4 Karyotype
Copyright © 2009 Pearson Education, Inc. When Does Mitosis Occur? Multicellular Organisms Growth Tissue repair Cell replacement of certain tissues (e.g. epidermis – skin) Single-celled Organisms Asexual reproduction
Copyright © 2009 Pearson Education, Inc. Mitosis Karyokinesis Genetic material is partitioned to daughter cells during nuclear division Cytokinesis Cytoplasmic division follows.
Copyright © 2009 Pearson Education, Inc. Cell Cycle
Copyright © 2009 Pearson Education, Inc. Mitosis Mitosis has discrete stages: prophase prometaphase metaphase anaphase telophase (see Figure 2.7)
Copyright © 2009 Pearson Education, Inc. Figure 2.7
Copyright © 2009 Pearson Education, Inc. Cohesin, Shugoshin, and Separase – 3 important protein complexes Shugoshin Cohesin
Copyright © 2009 Pearson Education, Inc. Cell-Cycle Regulation and Checkpoints
Copyright © 2009 Pearson Education, Inc. Cyclin-dependent Kinases Cell cycle is driven by enzymes called Cyclin-dependent kinases, or Cdk’s Kinases are enzymes that phosphorylate (add a phosphate group to) other proteins stimulates or inhibits protein’s activity Cdk’s are active only when they bind to other proteins called cyclins
Copyright © 2009 Pearson Education, Inc. Enzymes Drive the Cell Cycle Cell division occurs when growth factors bind to cell surface receptors, which leads to cyclin synthesis Cyclins then bind to and activate specific Cdk’s
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Activated Cdk’s Promote a variety of cell cycle events –Synthesis and activation of proteins required for DNA synthesis –Chromosome condensation –Nuclear membrane breakdown –Spindle formation –Attachment of chromosomes to spindle –Sister chromatid separation and movement
Copyright © 2009 Pearson Education, Inc. Meiosis Meiosis reduces the amount of genetic material by one-half to produce haploid gametes or spores containing one member of each homologous pair of chromosomes.
Copyright © 2009 Pearson Education, Inc. Meiosis Meiosis I and II each have prophase, metaphase, anaphase, and telophase stages (Figure 2.10).
Copyright © 2009 Pearson Education, Inc. Meiosis Prophase I has five substages, each including specific events (see Figure 2.9): leptonema zygonema pachynema diplonema diakinesis At the completion of prophase I, the centromeres of each tetrad structure are present on the equatorial plate.
Copyright © 2009 Pearson Education, Inc. Figure 2.9 Prophase I Additional Terms to Know: Synapse Bivalent Tetrad Crossing over
Copyright © 2009 Pearson Education, Inc. Figure 2.10 Meiosis
Copyright © 2009 Pearson Education, Inc. Meiosis II During meiosis II, the sister chromatids in each dyad are separated to opposite poles. Each haploid daughter cell from meiosis II has one member of each pair of homologous chromosomes.
Copyright © 2009 Pearson Education, Inc. Cohesin, Shugoshin, and Separase National Institute of Health Retrieved from Clift D, Marston AL - Cytogenet. Genome Res. (2011)
Copyright © 2009 Pearson Education, Inc. Disjunction and Nonjunction Disjunction Separation of homologous chromosomes Nondisjunction during meiosis I or II leads to gametes with abnormal numbers of chromosomes and can lead to abnormal offspring.
Copyright © 2009 Pearson Education, Inc. 2.5 The Development of Gametes Varies in Spermatogenesis Compared to Oogenesis
Copyright © 2009 Pearson Education, Inc. Section 2.5 Male gametes are produced by spermatogenesis in the testes (Figure 2.11). Female gametes are produced by oogenesis in the ovary.
Copyright © 2009 Pearson Education, Inc. Figure 2.11
Copyright © 2009 Pearson Education, Inc. Importance of Meiosis Mechanism of meiosis is basis for production of extensive genetic variation. Gametes receive either the maternal or the paternal chromosome from each homologous pair of chromosomes. An organism can produce 2 n (where n represents the haploid number) combinations of chromosomes in gametes.
Copyright © 2009 Pearson Education, Inc. Life Cycles Differ in Certain Organisms Diploid life cycle Ex. Humans and other animals Haploid life cycle Ex. Fungi, protists Alternation of generation Plants
Copyright © 2009 Pearson Education, Inc. The End