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Prophase I

Definition

noun

The first stage in the first meiotic division of meiosis. This stage is characterized by having five sub-stages namely leptotene, zygotene, pachytene, diplotene and diakinesis. It highlights the exchange of DNA between homologous chromosomes via a process called homologous recombination and the cross-over at chiasma(ta) between non-sister chromatids. Thus, this stage is important to increase genetic variation. This stage then ends with the disintegration of the nucleolus and the nuclear membrane.


Supplement

Since meiosis consists of two consecutive nuclear divisions, prophase occurs twice. Thus, there are prophase I and prophase II.


See also: prophase II, meiosis I


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Reproductive Systems-Follicle

... girl will already have about a million primary follicles . the primary oocytes will have started to divide by meiosis, but the process stops at prophase I FSH follicle stimulation hormone , and that hormone is secreted by the pituitary gland in the brain and its carried in the blood to the ovary, ...

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by Tamaroshka
Sat Nov 14, 2009 12:12 am
 
Forum: Human Biology
Topic: Reproductive Systems-Follicle
Replies: 3
Views: 53

Re: Questions about Prophase and Meiosis. Please Help.

Thanks for your help

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by MissAshley
Thu Nov 12, 2009 8:07 pm
 
Forum: Cell Biology
Topic: Questions about Prophase and Meiosis. Please Help.
Replies: 5
Views: 76

Questions about Prophase and Meiosis. Please Help.

... answers, but had no luck, so if anyone could help me I would greatly appreciate it. 1.If the chromosome content of one cell at the beginning of Prophase 1 is represented as in the accompanying figure, how many chromosomes does the cell contain? (Hint: As long as a chromosome consists of two ...

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by MissAshley
Wed Nov 11, 2009 8:22 pm
 
Forum: Cell Biology
Topic: Questions about Prophase and Meiosis. Please Help.
Replies: 5
Views: 76

How are chromosomes paired? Shape of Y chromosome?

... pairs and an XY “pair”. What is the shape of the Y-chromosome? (don't say Y). I'm thinking that in the early stages of mitosis and meiosis (early prophase?) the chromosome replicates its DNA and both strands are linked by the centromere. If this is true, then surely every chromosome before it ...

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by cliverlong
Tue Nov 03, 2009 12:17 pm
 
Forum: Genetics
Topic: How are chromosomes paired? Shape of Y chromosome?
Replies: 3
Views: 91

Re: Centromeres

So long as the chromatids are held together in the "X" shape, the centromeres are present. That stated, they would be around in prophase and metaphase. However, the centromeres are broken right down the middle when the sister chromatids are pulled apart in anaphase.

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by HylaCinerea
Tue Nov 03, 2009 2:09 am
 
Forum: General Discussion
Topic: Centromeres
Replies: 20
Views: 219
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