Thursday, November 19, 2009

Meiosis

Meiosis (not be confused with mitosis)

What: Formation of GAMETES. In this situation the parent cell has 46 chromosomes (diploid) and will eventually make 4 daughter cells with 23 chromosomes (haploid).
Where : sex cells

Meiosis has two stages, Meiosis 1 and Meiosis 2

The first stage of Meiosis is DIFFERENT from Mitosis.

Prophase 1
Chromosomes shorten and thicken
centrioles move to opposite poles

Metaphase 1
Homologous chromosomes (one from each parent) line up
Crossing over occurs (exchange of genetic material between homologous chromosomes)

Anaphase 1
Homolous chromosomes are pulled to opposite poles of the cell

Telophase and Cytokinesis 1
Nuclear membrane forms and two daughter cells are formed (each has 23 chromosomes duplicated)




Meiosis 2 - This process looks almost identical to mitosis, the difference is the number of chromosomes. Since meiosis 1 ended with each cell containing 23 duplicate chromosomes, that is how meiosis 2 will begin.

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