Mitosis to Meiosis

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Mitosis to Meiosis

• Sept. 8, 2005

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Meiosis Two Divisions

• How does Meiosis I differ from Mitosis?
• What kinds of regulatory systems would achieve
  the conversion of Mitosis into Meiosis I?

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Mitosis G1 and G2 Chromosomes
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Pairing of Homologs
Leptotene
Zygotene
Chromosome Axis (protein) with scaffolds and
loops of chromatin
Meiosis Zygotene Pairs of Homologs
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Kinetochore(chromatid structures)
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Cell Cycle Controls

• Cyclins (accelerators)
• Kinases (breaks)
• Hormones (initiators, inhibitors)
• DNA replication process
• DNA repair processes (p53 protein)
• Microtubule (Spindle) processes

• Forces to move chromosomes into homologus pairs
  (tetrads)
• Forces to uncoil, snip DNA, splice DNA, etc.

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Exchanges that give new combinations from
grandparents
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Linked LociShare a chromosome
What is necessary to have an exchange between
chromosomes?
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Crossing Over
Blue Loop displaces red DNA
Blue and red are non-sister chromatids that can
form a heteroduplex
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If a pairing happens where Base Pairs differ
NCO
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What new process appear?

• Pairing
• Enzymes to form pairing proteins
• Transport enzymes (proteins) into nucleus
• Location in right place, right amount and
  relationships
• Chromatid breaking, rejoining
• Enzymes to uncoil
• Enzymes to break
• Enzymes to join

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Centriole Dynamics
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Mitosis

• What happens in G1, S, G2?
• What is controlling the transitions?
• Explain how any process in the cell requires
  hundreds or thousands of genes.
• Give an example how timing of genes is as
  important as the products of the genes.
• How does Metaphase happen?
• How does Anaphase happen?

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Cyclins and Cell Cycle
Cell Cycle Model
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Mitosis
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Functional Groups of Genes
of genome
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Mitosis
Cell Cycle
Interphase G1
Interphase G2
Cell differentiation House-keeping processes
Synthesis for mitosis House-keeping
processes
Interphase S
Restriction Point
100s to 1,000s of sites initiate DNA replication
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Chromosome painting with fluorescent
antibodies specific for chromosome proteins
characteristic of each homologus pair
Polar view showing homologues in mitotic
metaphase
Nucleus
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Initiation ofAnaphase
(follows release of M-arrest)