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Chromosomes, Mitosis, and Meiosis

Chromosomes, Mitosis, and Meiosis. In Humans…. 23 chromosomes donated by each parent 46 chromosomes in total or 23 pairs 44 autosomes and 2 sex chromosomes. Autosomes determine somatic (body) traits Sex chromosomes determine traits linked to gender. Figure 1: Human karyotype. Boy or Girl?.

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Chromosomes, Mitosis, and Meiosis

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  1. Chromosomes, Mitosis, and Meiosis

  2. In Humans… • 23 chromosomes donated by each parent • 46 chromosomes in total or 23 pairs • 44 autosomes and 2 sex chromosomes Autosomes determine somatic (body) traits Sex chromosomes determine traits linked to gender Figure 1: Human karyotype

  3. Boy or Girl? The Y Chromosome Decides Y - Chromosome X - Chromosome

  4. Chromosome Pairs • A pair of chromosomes is called a ‘homologous pair’ • Homologous pairs have the same genes but not necessarily the same alleles • X and y also form a homologous pair

  5. Sex cells or Gametes (sperm/ova): • Contain 23 chromosomes: 22 autosomes and 1 sex chromosome. • One chromosome from each homologous pair is randomly selected during sex cell formation • Sex cells are haploid (haploid number “n” = 23 in humans). • Fertilization results in zygote with 2 haploid sets of chromosomes - now diploid. • Diploid cell; 2n = 46. (n=23 in humans)

  6. Chromosome Numbers

  7. Meiosis • Most cells in the body are produced by mitosis. • Only gametes are produced by meiosis. • What is the point of meiosis? • produce a cell with half the number of chromosomes! • increase genetic variability in offspring!

  8. Mitosis vs. Meiosis

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