Meiosis is reduction division that occurs only in germ cells where gametes are produced with half the chromosome number to that of the parent cell. This reduction is essential for maintenance of chromosome number in a species.
Major events in meiosis
1) Two successive cell division without DNA replication
2) Formation of chiasmata and crossing over that lead to genetic variation
3) Separation of homologous chromosomes in anaphase I of meiosis I
4) Separation of sister chromatids in anaphase II of meiosis II
- The two members of each bivalent repel each other and move towards the opposite poles.
- Each pole receives half the number of chromosomes.
- Reduction occurs and movement of chromosomes is brought by the spindle fibres.
- The centromere divides and two chromatids of each chromosome separate and move towards the poles.
- It is similar to mitosis. Each pole has same number of chromosomes, but with a single chromatid.
- After separation each chromatids become chromosome.
The major difference is
- In anaphase I of meiosis I, homologous chromosomes are separated
- In anaphase II of meiosis II, sister chromatids are separated