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Why are oocytes much more likely to have associated chromosomal abnormalities than sperm?
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Correct answer:
Oocytes are arrested in prophase 1 of meiosis until ovulation occurs and causes these cells to enter metaphase 1. Thus, the genetic material of oocytes has already been duplicated and exists in homologous chromosome pairs for multiple years before it becomes fertilized, leaving much more time for chromosomal abnormalities to occur. Male primordial germ cells, on the other hand, are reactivated at puberty as spermatogonial stem cells to enter mitosis. From these stem cells, spermatogonia are produced and replicate to enter meiosis 1 and 2 and produce haploid sperm. Thus, new spermatogonial stem cells are constantly entering the spermatogenic cycle, leaving far less time for chromosomal abnormalities to occur once fertilization occurs.
