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 SCHOOL OF VETERINARY MEDICINE
Oogenesis

 

Meiosis
  • Cellular division resulting in the formation of gametes.
  • Consists of two nuclear divisions.
  • Results in one gamete each containing 1N chromosomes,
Prophase
  • Leptotene - pairing of diploid chromosomes
  • Zygotene - transitory pairing stage
  • Pachytene - genetic exchange between chromosomes
  • Diplotene - resting stage at which oocytes arrest in primordial follicles.
  • Diakinesis or germinal vesicle stage - meiosis resumes in the Graffian follicle. Caused by the LH from the anterior pituitary.
Metaphase I
  • Bivalents arranged on microtubules. Cell divides to contain 2 1N chromosomes.
  • Anaphase - bivalents move to opposite poles. Dog, fox and horse ovulate this structure.
Metaphase II and polar body extrusion
  • A 1N chromosome is expelled (the polar body) to leave the cell 1 1N chromosome in the secondary oocyte.
  • This is the ovulated structure in most species.

contributed by Bruce E Eilts on  12-July-2000
modified by on 25 July 2006




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