meiosis sexual reproduction. why is meiosis important? make eggs and sperm for reproduction genetic...
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Meiosis
Sexual Reproduction
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Why is meiosis important?
• Make eggs and sperm for reproduction• Genetic diversity – half DNA from father and
half from mother= new combination
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• Somatic cells – (any cell other than egg or sperm)-formed from mitosis only -– Have 46 chromosomes and divide to make
identical cells with 46 chromosomes– Diploid (2n)
• Gametes (egg and sperm) – formed from meiosis only– Have 23 chromosomes– Haploid (n)
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• Autosomes are the 22 pairs (44) of chromosomes that are not involved in determining gender
• Sex chromosomes are the pair (2) that determine gender
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• Homologous chromosomes- pair of chromosomes that are similar in size, shape, and genetic content- one in each pair comes from the father and the other from the mother.
• Humans have ____pairs of homologous chromosomes.
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Chromosome Numbers in Cells• Diploid (2n) cell contains 2 sets of
chromosomes (somatic cell)• Haploid (n) cell contains 1 set of chromosome
(gamete)• What happens when 2 haploid cells fuse in
fertilization?
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Homologous Chromosomes and Sister chromatids
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Mitosis vs Meiosis
• Mitosis – used for Growth– Two daughter cells– genetically identical to parent cell– two full sets of chromosomes (diploid)– makes bigger organism
• Meiosis – used for Reproduction– Four daughter cells– genetically different from parent cell (and each other)– one full sets of chromosomes (haploid)– helps makes another organism (sexual reproduction)
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Meiosis- two cell divisionsMeiosis preceded by an interphase (just like mitosis) – chromosomes replicated during the S phase.
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Meiosis 1
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Stages of Meiosis
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Crossing Over
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Crossing Over in ActionWhat is the advantage of crossing over?
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How does this differ from metaphase in mitosis?
Mitos is
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Independent Assortment
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After the 1st Division
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• http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter28/animation__unique_features_of_meiosis.html
• Features unique to meiosis
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Mitosis versus Meiosis
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What happens to the possible combinations when crossing over occurs?
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Sperm versus the Egg