How does chromosome number get halved in meiosis I?

  • #1
navneet9431
Gold Member
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8

Main Question or Discussion Point

In meiosis 1, it is said that chromosome numbers become halved in the two daughter cells.
For example, in a 2n human cell there are 46 chromosomes.
During meiosis 1, the cell will undergo interphase and probably the S-phase, where chromosome number becomes duplicated.
Now the cell is 4n (i.e. 92 chromosomes). During anaphase 1, 46 chromosome out of 92 would go towards one pole and 46 would go opposite.
Thus the resulting two cells will have 46 chromosomes in each. So why should we say that, in meiosis 1, the chromosome number is reduced?
 

Answers and Replies

  • #2
atyy
Science Advisor
13,732
1,871
During meiosis 1, the cell will undergo interphase and probably the S-phase, where chromosome number becomes duplicated.
Now the cell is 4n (i.e. 92 chromosomes).
The stages before meiosis are similar to those of interphase before mitosis. The number of chromosomes does not double before meiosis I. Before meiosis I, the number of chromosomes remains the same, but each chromosome doubles the number of its chromatids.

http://cyberbridge.mcb.harvard.edu/mitosis_4.html
http://cyberbridge.mcb.harvard.edu/mitosis_6.html
 

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