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Understanding Meiosis: Cell Division Process and Genetic Variation

Explore Meiosis, a fundamental process reducing chromosomes, generating haploid cells, and promoting genetic diversity through recombination. Learn about stages like Prophase I, Metaphase I, and Anaphase I, distinct from mitosis.

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Understanding Meiosis: Cell Division Process and Genetic Variation

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  1. Meiosis 8.3 (p. 153-156) Meiosis = cell division that reduces the number of chromosomes in half • Diploid number to haploid number • Gametes = sex cells; have haploid number (male: sperm, female: egg) • Like a double mitosis: PMAT I and PMAT II, with some key differences Diploid = Haploid =

  2. Meiosis 8.3 (p. 153-156) Prophase I = homologous chromosomes pair up • Called synapsis; chromosome pairs called tetrads (tetra = 4) • Crossing-over = chromatids swap genes; happens sometimes causing genetic variation • Genetic recombination = new mix of genes from crossing-over

  3. Meiosis 8.3 (p. 153-156) Metaphase I = tetrads line up along the equator • Homologous pairs line up next to each other • Key difference

  4. Meiosis 8.3 (p. 153-156) Anaphase I = homologous chromosomes move to opposite poles • Big difference: each chromosomes still has 2 chromatids • That is the centromeres don’t split

  5. Meiosis 8.3 (p. 153-156) TelophaseI = 2 cells separate, but now each cell has haploid number of chromosomes

  6. Meiosis 8.3 (p. 153-156) PMAT II = looks very much like mitosis but at the end it has haploid number (1n) • Single chromatid is not copied during an interphase stage • Instead these gametes will match up chromatids when they fuse with another sex cell • Zygote = sperm and egg fused to form new cell again with diploid number (2n)

  7. Meiosis 8.3 (p. 153-156) Sexual reproduction = reproduction by forming a zygote (male and female) • Offspring is genetically unique Asexual reproduction = reproduction from one parent • By binary fission or mitosis only, no meiosis • Offspring is genetically identical to parent

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