The purpose of meiosis
a) is to reduce the normal diploid cells (2 copies of each chromosome / cell) to haploid cells, called gametes (1 copy of each chromosome per cell).
In humans, these special haploid cells resulting from meiosis are eggs (female) or sperm (male).
In yeast cells, they are spores.
To carry out this specialized process, the cells duplicate their DNA but follow this by two rounds of division, instead of one. The first division separates the duplicated homologues from each other. This essentially reduces the number of chromosomes in each cell. Thus, we call this the reductional, or Meiosis I division.
The second division operates similarly to the mitotic division, and separates the sister chromatids from one another; we call this the equational, or Meiosis II division. The offspring from meiosis have half the number of chromosomes as their parent cell, because they receive just one copy of each chromosome, rather than two. (Compare the offspring in the meiosis diagram to those in mitosis).
This is a nice article, it has been of immense help to me during my 300 level Biochemistry examination. Thanks a million times.
ReplyDeletethanks a lot. i have been away from Biological Sciences for over 20 years but this explanation of meiotic cell division brings back to my memory almost in a graphic form, my years of study, in both BS and MS levels in Botany. I really appreciate
ReplyDeleteThankyou for making this process clear for my son doing his gcse bilogy.
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