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CH 8

CH 8. Reproduction and Inheritance. LM 340 . Reproduction. Asexual Reproduction Sexual Reproduction. Duplication of chromosome and separation of copies. 1. Continued elongation of the cell and movement of copies. 2. Division into two daughter cells. 3. Prokaryotes are asexual.

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CH 8

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  1. CH 8 Reproduction and Inheritance

  2. LM 340 Reproduction • Asexual Reproduction • Sexual Reproduction

  3. Duplication of chromosomeand separation of copies 1 Continued elongation of thecell and movement of copies 2 Division intotwo daughter cells 3 Prokaryotes are asexual Plasmamembrane Prokaryoticchromosome • Via binary fission • Recall that Prokaryotes have circular DNA Cell wall Prokaryotic chromosomes Figure 8.3A

  4. LM 600 Eukaryotes • Complex cell division • Chromosomes occur as chromatin unless dividing • Individual chromosomes visible when cell is dividing

  5. Cell cycle • Ordered sequence of events from time a cell is first formed until its own division • Growth phase • Division phase (mitotic phase) • Mitosis • Cytokinesis

  6. INTERPHASE S (DNA synthesis) G1 Fig. 8-5 G2 Cytokinesis Mitosis MITOTIC PHASE (M)

  7. Fig. 8-6a PROPHASE PROMETAPHASE INTERPHASE Chromatin Centrosome Fragments of nuclear envelope Early mitotic spindle Centrosomes (with centriole pairs) Kinetochore Centromere Plasma membrane Spindle microtubules Nuclear envelope Chromosome, consisting of two sister chromatids Nucleolus

  8. Fig. 8-6b METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS Nucleolus forming Cleavage furrow Metaphase plate Nuclear envelope forming Daughter chromosomes Spindle

  9. Cytokenesis • Cleavage furrow • Microfilaments contract Cleavage furrow Cleavage furrow Contracting ring of microfilaments Daughter cells

  10. Cell plate forming Daughter nucleus Wall of parent cell Plant cellsCell plate New cell wall Cell wall Vesicles containing cell wall material Daughter cells Cell plate

  11. Cell Division • Growth factors • Density-Dependent inhibition • Anchorage dependence

  12. Growth • Cell cycle control system • Set of molecules that triggers and coordinates key events in cell cycle G1 checkpoint G0 Control system S G1 M G2 M checkpoint G2 checkpoint

  13. Growth factor Plasma membrane Fig. 8-9b Relay proteins Receptor protein G1 checkpoint Signal transduction pathway Control system G1 S G2 M

  14. Out of control • Cancer • Do not respond to cell control system • No density-dependent inhibition • Divide indefinitely

  15. Meiosis terms • Somatic cells • Homologous chromosomes • Sex chromosomes • Autosomes • Diploid • Haploid

  16. Haploid gametes (n = 23) n Egg cell n Sperm cell Fig. 8-13 Meiosis Fertilization Diploid zygote (2n = 46) 2n Multicellular diploid adults (2n = 46) Mitosis and development

  17. Meiosis • Produces haploid gametes in diploid organisms • Duplication of chromosomes • Two cell divisions

  18. MEIOSIS I: Homologous chromosomes separate METAPHASE I PROPHASE I ANAPHASE I INTERPHASE Fig. 8-14a Centrosomes (with centriole pairs) Microtubules attached to kinetochore Sister chromatids remain attached Metaphase plate Sites of crossing over Spindle Tetrad Nuclear envelope Centromere (with kinetochore) Sister chromatids Homologous chromosomes separate Chromatin

  19. MEIOSIS II: Sister chromatids separate TELOPHASE II AND CYTOKINESIS TELOPHASE II AND CYTOKINESIS PROPHASE I METAPHASE II ANAPHASE II Fig. 8-14b Cleavage furrow Haploid daughter cells forming Sister chromatids separate

  20. MITOSIS MEIOSIS Parent cell (before chromosome duplication) Site of crossing over MEIOSISI Prophase I Prophase Tetrad formed by synapsis of homologous chromosomes Duplicated chromosome (two sister chromatids) Chromosome duplication Chromosome duplication 2n = 4 Fig. 8-15 Tetrads align at the metaphase plate Chromosomes align at the metaphase plate Metaphase I Metaphase Anaphase I Telophase I Anaphase Telophase Sister chromatids separate during anaphase Homologous chromosomes separate (anaphase I); sister chroma- tids remain together Haploid n = 2 Daughter cells of meiosis I No further chromosomal duplication; sister chromatids separate (anaphase II) MEIOSISII 2n 2n Daughter cells of mitosis n n n n Daughter cells of meiosis II

  21. Diversity • Random arrangement of homologous chromosomes • Different gene versions • Genetic recombination • “Crossing over”

  22. Abnormal sex chromosomes • Trisomy 21 Error Nondisjunction in meiosis I Normal meiosis II Gametes n + 1 n + 1 n – 1 n – 1 Number of chromosomes

  23. Error • Down syndrome • Extra copy of chromosome 21

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