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Chromosomes

Chromosomes. Human Chromosomes. Human cells have 23 pairs of chromosomes ( homologous pairs ) for a total of 46. One member of each pair comes from the sperm and the other from the egg. Each chromosome in the homologous pair will contain the same genes (possibly different alleles). Mitosis.

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Chromosomes

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  1. Chromosomes

  2. Human Chromosomes • Human cells have 23 pairs of chromosomes (homologous pairs) for a total of 46. • One member of each pair comes from the sperm and the other from the egg. • Each chromosome in the homologous pair will contain the same genes (possibly different alleles)

  3. Mitosis

  4. Mitosis • Mitosis is the process in which a cell duplicates its chromosomes and divides to generate two identical cells. • Occurs when organisms grow (ie from a zygote to adult) and also in wound healing. (growth and repair) • Happens throughout the body, but particularly in bone marrow, skin, hair and nails.

  5. Sequence of Events • Before mitosis occurs, DNA must replicate. • Chromatin in the nucleus begins to condense and becomes visible as chromosomes. Chromosome Chromatin

  6. The Mitosis Process

  7. Sequence of Events • Each chromosome forms an identical pairthat remains attached at theCentromere. Centrioles begin moving to opposite ends of the cell. • The nuclear membrane dissolves as centrioles send out spindle fibres to attach to the centromeres.

  8. Centromere Unduplicated Duplicated

  9. Sequence of Events • Spindle fibres align the chromosomes along the middle of the cell nucleus. • The paired chromosomes separate at the centromere and move to opposite sides of the cell. • Chromosomes arrive at opposite poles and the cell begins to divide into two.

  10. 46 chromosomes

  11. 92 chromosomes

  12. 46 chromosomes 46 chromosomes +

  13. Mitosis

  14. Mitosis

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