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Write a Note on Meiosis

Note on Meiosis

 

Meiosis can be divided into two parts:

 

1. i) Meiosis-I
2. ii) Meiosis-II

 

Meiosis-I:

 

It has following stages:

 

Prophase-I:

 

1. i) It is very lengthy and important phase.

 

1. ii) It is divided into 5 more sub-phases.

 

iii) Its important process in Synapsis in which homologous chromosomes begins to pair lengthwise.

 

1. iv) Each pair consists of four chromatids.

 

1. v) After Synapsis crossing over takes place. (in which chromosomes exchange their chromatids)

 

Metaghase-II:

 

1. i) The centromere of the homologous chromosomes arranges themselves on equator.

 

Anaphase-I:

 

1. i) In this phase homologous chromosomes begins to separate.

 

1. ii) The spindle fiber contract.

 

iii) Half of the chromosomes move towards each pole.

 

 

Telophase-I:

 

1. i) Half chromosomes reached towards their opposite poles.

 

1. ii) Chromosomes again become elongated.

 

iii) Nuclear membrane and nucleoli are reformed.

 

1. iv) Two daughter nuclei are formed.

 

Meiosis-II:

 

This division is similar to mitosis. At the end of this stage four daughter cells are formed which afterwards change into spores (in plants) or gametes (in animals)

 

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