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about human fertilization

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about human fertilization

Postby MrMistery » Sun Jun 04, 2006 10:03 am

Ok, so i'm studying the reproductive function. And i understand that the human secondary ovocyte is arrested at metaphase II. Then it is released and becomes the mature ovum, completing meiosis only after it is fertilised. Then, 20 pages later, they tell me that the ovum has no centrosome, and that it uses the sperm bazal body to create a centrosome around it, replicate it and complete division.
So, can someone please explain to me, how can the ovum be at metaphase II without having a centrosome? Don't you need to have 2 centrosomes and a spindle to be able to call it metaphase?!
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
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Postby Doc44 » Sun Jun 04, 2006 4:47 pm

One centrosome gives rise to or is made up of two centrioloes.

Metaphase...centrioles arive at the poles of the cell and the chromosomes (centromeres) line up on the equitorial plate with spindle fibers and aster rays visible in cytoplasm.

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Postby baikuza » Mon Jun 12, 2006 5:14 am

i think that, in this topic, not only centrioles can do the job as the aster in the cell when the cell is in the mitosis or meiosis... i will said that some thing that have a great "attraction" on spindel occurs. this matterial replace the centrioles to do that... just the same like in the plant cell, even it has centrosome but do not have centriole.... an site said this... "Plant cells, on the other hand, are acentriolar and therefore lack an obvious centrosome..." but they can do mitosis..all the phase.. so maybe this is the same in the ovum-but this is animal cell...i do not know for sure, but if "they" whom Mr. Mistery said above and it is the reality.. i will said that it maybe the same as happen in plant cell
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