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Gametogenesis

Gametogenesis. Gametogenesis. Gametogenesis is the creation of gametes. In males, it is spermatogenesis , creation of sperm. In females, it is oogenesis , creation of ova. Spermatogenesis. Occurs in the testes.

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Gametogenesis

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  1. Gametogenesis

  2. Gametogenesis • Gametogenesis is the creation of gametes. • In males, it is spermatogenesis, creation of sperm. • In females, it is oogenesis, creation of ova.

  3. Spermatogenesis • Occurs in the testes. • Meiosis occurs and the result is four, non-identical cells, each with 23 chromosomes that will develop into sperm.

  4. Oogenesis • Occurs in the ovaries and in the oviducts. • After Telophase I and II, the cytoplasm is not equally divided. • One of the new cells gets the majority and it survives, while the other one, a polar body, gets broken down.

  5. Key Terms • Diploid: Having the full chromosome number (46 in humans). • Haploid: Having half the full chromosome number (23 in humans).

  6. Karyotype • A karyotype is a pictorial representation of a person’s chromosomes. • An example is shown to the right.

  7. Karyotype • The X and Y chromosomes are known as the sex chromosomes. • They determine a person’s gender. • XX is female, while XY is male. • It is the dad who determines the baby’s gender as he can produce sperm carrying the X chromosome or sperm carrying the Y chromosome.

  8. Non-Disjunction

  9. Non-disjunction • Non-disjunction is the failure of chromosomes (or tetrads) to separate during anaphase I or II in meiosis. • The resulting cells will not have the correct number of chromosomes.

  10. Non-disjunction • If it happens in meiosis I, all the resulting cells will be affected. If it happens in meiosis II, only half will be affected.

  11. Having extra chromosomes is bad! • Having too many or too few chromosomes is a bad thing. • Down Syndrome is caused by having an extra chromosome 21.

  12. Having extra chromosomes is bad! • Klinefelter’s Syndrome occurs when an individual receives two X chromosomes and a Y chromosome. • The result is an infertile male with varying degrees of feminity.

  13. Missing chromosomes is bad! • Turner Syndrome occurs when the individual only gets one sex chromosome, an X, from their mother. • The result is an infertile female with a broad chest, poor breast development, low set ears, short stature and poor hearing amongst other things.

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