When the Cells Divide Again What Happens to the Number of Chromosomes in Meiosis

Meiosis is a procedure where a unmarried prison cell divides twice to produce iv cells containing half the original corporeality of genetic information. These cells are our sex activity cells – sperm in males, eggs in females.

• During meiosis one cell divides twice to course iv daughter cells.
• These iv daughter cells only have half the number of chromosomes of the parent cell – they are haploid.
• Meiosis produces our sex cells or gametes (eggs in females and sperm in males).

Meiosis tin be divided into 9 stages. These are divided between the first fourth dimension the cell divides (meiosis I) and the second time it divides (meiosis II):

Meiosis I

1. Interphase:

• The Dna in the cell is copied resulting in 2 identical full sets of chromosomes.
• Exterior of the nucleus are two centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division.
• During interphase, microtubules extend from these centrosomes.

2. Prophase I:

• The copied chromosomes condense into X-shaped structures that can be hands seen under a microscope.
• Each chromosome is composed of two sister chromatids containing identical genetic data.
• The chromosomes pair upward so that both copies of chromosome 1 are together, both copies of chromosome ii are together, and and then on.
• The pairs of chromosomes may and so exchange bits of Dna in a process chosen recombination or crossing over.
• At the terminate of Prophase I the membrane effectually the nucleus in the cell dissolves away, releasing the chromosomes.
• The meiotic spindle, consisting of microtubules and other proteins, extends beyond the jail cell between the centrioles.

3. Metaphase I:

• The chromosome pairs line upward side by side to each other along the centre (equator) of the jail cell.
• The centrioles are at present at opposites poles of the prison cell with the meiotic spindles extending from them.
• The meiotic spindle fibres attach to i chromosome of each pair.

iv. Anaphase I:

• The pair of chromosomes are then pulled autonomously past the meiotic spindle, which pulls 1 chromosome to one pole of the cell and the other chromosome to the reverse pole.
• In meiosis I the sis chromatids stay together. This is different to what happens in mitosis and meiosis II.

5. Telophase I and cytokinesis:

• The chromosomes consummate their move to the contrary poles of the prison cell.
• At each pole of the cell a full set of chromosomes get together together.
• A membrane forms around each fix of chromosomes to create 2 new nuclei.
• The single cell so pinches in the middle to form ii separate daughter cells each containing a full set of chromosomes inside a nucleus. This process is known as cytokinesis.

Meiosis II

six. Prophase Ii:

• At present there are two daughter cells, each with 23 chromosomes (23 pairs of chromatids).
• In each of the ii daughter cells the chromosomes condense again into visible X-shaped structures that can exist easily seen nether a microscope.
• The membrane around the nucleus in each daughter cell dissolves away releasing the chromosomes.
• The centrioles duplicate.
• The meiotic spindle forms once more.

7. Metaphase II:

• In each of the ii daughter cells the chromosomes (pair of sister chromatids) line upwardly end-to-cease along the equator of the prison cell.
• The centrioles are now at opposites poles in each of the daughter cells.
• Meiotic spindle fibres at each pole of the jail cell adhere to each of the sister chromatids.

8. Anaphase II:

• The sister chromatids are and then pulled to opposite poles due to the activity of the meiotic spindle.
• The separated chromatids are at present individual chromosomes.

9. Telophase II and cytokinesis:

• The chromosomes complete their move to the contrary poles of the cell.
• At each pole of the jail cell a full set of chromosomes gather together.
• A membrane forms around each set of chromosomes to create ii new cell nuclei.
• This is the last phase of meiosis, yet cell division is not complete without another round of cytokinesis.
• In one case cytokinesis is complete there are 4 granddaughter cells, each with one-half a set of chromosomes (haploid):
  • in males, these four cells are all sperm cells
  • in females, ane of the cells is an egg jail cell while the other three are polar bodies (pocket-size cells that do non develop into eggs).

Illustration showing the nine stages of meiosis.
Image credit: Genome Research Limited

This folio was concluding updated on 2021-07-21

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Source: https://www.yourgenome.org/facts/what-is-meiosis

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