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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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Chromosome segregation

... importance of each of these concepts. I know that genetic recombination is a process that occurs in the first meiotic division, specify in prophase I (subphase: pachytene), and consists of the intersection of two of the four chromatids of homologous chromosomes to form a bivalent, beginning ...

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by Fidias
Mon Jun 07, 2010 4:46 pm
 
Forum: Cell Biology
Topic: Chromosome segregation
Replies: 1
Views: 209

Meiosis = extreme confusion. Please help!

... don't get too confused by the terms "chromosome" and "chromatid". Chromosome can refer to both 1.) the X shape you see during prophase and metaphase, which is two chromatids joined by a centromere, and 2.) a single piece of coiled DNA in a cell (so a human cell has 23 pairs ...

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by mamoru
Tue Mar 02, 2010 2:27 pm
 
Forum: Cell Biology
Topic: Meiosis = extreme confusion. Please help!
Replies: 6
Views: 2236

Meiosis

I don't get this. . .How can crossing over occur in prophase 1 when gametes don't meet until meiosis II? Please clarify. Thanks.

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by mutt13
Thu Feb 25, 2010 8:54 am
 
Forum: Human Biology
Topic: Meiosis
Replies: 2
Views: 254

Re: Question regarding meiosis and ploidity

... and the result is 4 haploid cells. Here, perhaps seeing it as an example using A and B for a homologous pair would work: Start: AB Replication and Prophase and Metaphase of Meiosis I: AABB Anaphase and Telophase of Meiosis I: AA BB Anaphase and Telophase of Meiosis II: A A B B Make sense?

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by mamoru
Thu Feb 25, 2010 5:11 am
 
Forum: Cell Biology
Topic: Question regarding meiosis and ploidity
Replies: 2
Views: 200

Re:

... chromosome at that point. Then, what you see is replication (which in real life would then be followed by the supercoiling into Chromosomes during Prophase), which gives the well-known X shape of the chromosome (it is actually two copies of the same chromosome attached together). So, in the second ...

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by mamoru
Tue Feb 23, 2010 12:33 am
 
Forum: Genetics
Topic: Do Chromosomes dissolve and disappear?
Replies: 4
Views: 412
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