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Gametogenesis

Gametogenesis. Sex Cell Formation in Humans. Spermatogenesis. Production of sperm by meiosis Meiosis occurs in the seminiferous tubules of the testes Sperm cells mature and are stored in the epididymis until ejaculation Males can produce sperm their entire life.

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Gametogenesis

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  1. Gametogenesis Sex Cell Formation in Humans

  2. Spermatogenesis • Production of sperm by meiosis • Meiosis occurs in the seminiferous tubules of the testes • Sperm cells mature and are stored in the epididymis until ejaculation • Males can produce sperm their entire life Figure 1: Cross-section of testicle

  3. Oogenesis • Production of eggs (or ova) • Occurs in the follicles of the ovary

  4. Oogenesis • A female infant has all of the egg cells she will ever have (~ 2 million), but most die before reproductive age. • About 300 000 remaining at sexual maturity (~ age 12), but are dying constantly • 400-500 released during reproductive years, until the supply runs out

  5. Oogenesis • All cells are in prophase I of meiosis • During the menstrual cycle, one cell progresses through meiosis, but the process is halted at metaphase II • The cell remains in metaphase II, unless it is fertilized by a sperm cell; only then will second division be completed.

  6. Microscope Activity • Examine slides of sperm and ova; construct a proper scientific drawing of each • Compare the size of both cells. Estimate how many times larger one cell is than the other. • Suggest reasons why one cell is much larger than the other (consider the role of each cell in fertilization) • Explain why gametogenesis produces 4 viable sperm cells but only one egg cell.

  7. Meiosis KM

  8. Crossing over Chiasmata – sites of crossing over, occur in synapsis. Exchange of genetic material between non-sister chromatids. Crossing over produces recombinantchromosomes. Meiosis KM

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