Question

What are the steps of meiosis?

Answer 1

Meiosis:

Meiosis is the reduction division in which the chromosome number is reduced to half.

It occurs during the production of gametes - egg and sperm.

Stages of meiosis:

Meiosis I:

During this stage of division the homologous chromosome separate.

Meiosis II:

During this stage sister chromatids are separated.

Meiosis I:

Interphase – the cell grows as in mitosis during G1 phase, DNA replication occurs and copies all its chromosomes during S phase, and gets ready for cell division during the G2 phase.

Prophase I:

During this stage the homologous chromosomes pair and exchange of DNA between two non sister chromatids - crossing over takes place.

Prophase I has following stages:

Leptotene:

During this stage the sister chromatids are present close to each other, they are visible thin threads inside the nucleus.

Zygotene:

During this stage the homologous chromosomes pair each other and synapse of the homologous chromosome takes place.

Pachytene:

During this stage the chromosomal crossing over takes place between the non sister chromatids.

Diplotene:

During this stage the homologous chromosomes separate from each other.

Diakinesis:

During this stage the chromosomes condenses further.

• The nuclear membrane disintegrates.
• Meiotic spindle appears.
• Nucleoli disappears.

Metaphase I:

• The homologous chromosomes align along the metaphase plate.
• Microtubule from the meiotic spindle attach to the kinetochore of the centromere of each homologous chromosome.

Anaphase I:

• The microtubules pull the homologous chromosomes to opposite poles.
• The homologous chromosomes are separated.

Telophase I:

• The homologous chromosomes arrive at opposite pole, each has pair of chromatids.
• Spindle disappears.
• Nuclear membrane appears around the haploid set of chromosome.
• Chromosomes forms the chromatids.
• Cytokinesis occurs to form two daughter cells.

Interkinesis:

Between meiosis I and meiosis II the cells enter the stage of rest known as the interkinesis.

Meiosis II:

This involves the separation of the sister chromatids.

Prophase II:

• The nucleoli and nuclear membrane disappears.
• The chromatids condenses.
• Spindle fiber appears for the next division

Metaphase II:

The centromere attach to the spindle fibers.

Anaphase II:

The kinetochores separate, the sister chromatids get separated to the opposite poles.

Telophase II:

• Spindle fiber disappears.
• Nuclear membrane appears.
• Cytokinesis takes place which forms the four daughter cells with haploid set of chromosomes.