Cell Division

MEIOSIS

Meiosis involves two sequential cycles of nuclear and cell division, but only a single cycle of DNA replication. Meiosis is divided into meiosis I and meiosis II.

Meiosis IMeiosis II
Prophase IProphase II
Metaphase IMetaphase II
Anaphase IAnaphase II
Telophase ITelophase II

MEIOSIS I

Prophase I:

Prophase in meiosis I is typically longer and more complex than the prophase in meiosis II. Prophase I is subdivided into five phases, viz. Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis.

Leptotene:
leptotene
Zygotene:
zygotene
Pachytene:
pachytene
Diplotene:
diplotene

Diakinesis:

Metaphase I:

Anaphase I:

Homologous chromosomes separate, but sister chromatids remain attached at their centromeres.

Telophase I:

The stage between the two meiosis divisions is called interkinesis. Interkinesis is usually short lived.


MEIOSIS II

Prophase II: Meiosis II resembles the mitotic cell division. It begins immediately after cytokinesis. Nuclear membrane disappears. Chromosomes again become compact.

Metaphase II: The chromosomes align at the equator. Spindle fibres from the opposite poles get attached to the kinetochores of sister chromatids.

Anaphase II: Centromeres split and sister chromatids move towards the opposite poles.

Telophase II: The two groups of chromosomes get enclosed by nuclear envelope. This is followed by cytokinesis; resulting in the formation of four daughter cells.

Significance of Meiosis:

Difference Between Mitosis and Meiosis
MitosisMeiosis
This type of division takes place in somatic cells.This type of division takes place in gametic cells.
Two daughter cells are formed.Four daughter cells are formed.
Number of chromosomes remains diploid in daughter cells.Number of chromosomes becomes haploid in daughter cells.
Mitosis is necessary for growth and repair.Meiosis is necessary for sexual reproduction.
Crossing over does not take place.Crossing over takes place.


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