Meiosis Is the Process by Which a Cell Divides and Then Divides Again

Meiosis is a process where a single jail cell divides twice to produce 4 cells containing one-half the original amount of genetic information. These cells are our sexual activity cells – sperm in males, eggs in females.

• During meiosis one cell divides twice to form 4 daughter cells.
• These 4 daughter cells just have one-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 exist divided into nine stages. These are divided between the commencement time 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 total sets of chromosomes.
• Outside of the nucleus are 2 centrosomes, each containing a pair of centrioles, these structures are critical for the process of cell division.
• During interphase, microtubules extend from these centrosomes.

two. Prophase I:

• The copied chromosomes condense into X-shaped structures that tin can be easily seen under a microscope.
• Each chromosome is equanimous of 2 sister chromatids containing identical genetic information.
• The chromosomes pair up so that both copies of chromosome 1 are together, both copies of chromosome 2 are together, and and so on.
• The pairs of chromosomes may then exchange bits of DNA in a process called recombination or crossing over.
• At the end of Prophase I the membrane around the nucleus in the jail cell dissolves away, releasing the chromosomes.
• The meiotic spindle, consisting of microtubules and other proteins, extends across the cell betwixt the centrioles.

3. Metaphase I:

• The chromosome pairs line upwardly next to each other along the centre (equator) of the jail cell.
• The centrioles are at present at opposites poles of the cell with the meiotic spindles extending from them.
• The meiotic spindle fibres adhere to 1 chromosome of each pair.

4. Anaphase I:

• The pair of chromosomes are then pulled apart by the meiotic spindle, which pulls one chromosome to i pole of the cell and the other chromosome to the opposite pole.
• In meiosis I the sis chromatids stay together. This is different to what happens in mitosis and meiosis Ii.

v. Telophase I and cytokinesis:

• The chromosomes complete their move to the contrary poles of the 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 then pinches in the centre to grade two split up daughter cells each containing a full set of chromosomes within a nucleus. This process is known as cytokinesis.

Meiosis Two

half dozen. Prophase II:

• Now there are two daughter cells, each with 23 chromosomes (23 pairs of chromatids).
• In each of the two daughter cells the chromosomes condense again into visible X-shaped structures that can be easily seen nether a microscope.
• The membrane around the nucleus in each daughter cell dissolves abroad releasing the chromosomes.
• The centrioles indistinguishable.
• The meiotic spindle forms again.

seven. Metaphase II:

• In each of the two daughter cells the chromosomes (pair of sister chromatids) line up end-to-end along the equator of the cell.
• The centrioles are now at opposites poles in each of the daughter cells.
• Meiotic spindle fibres at each pole of the cell attach to each of the sister chromatids.

viii. Anaphase II:

• The sis chromatids are and then pulled to opposite poles due to the action of the meiotic spindle.
• The separated chromatids are now private chromosomes.

ix. Telophase 2 and cytokinesis:

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

Illustration showing the nine stages of meiosis.
Prototype credit: Genome Inquiry Limited

This page was concluding updated on 2021-07-21

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Source: https://www.yourgenome.org/facts/what-is-meiosis#:~:text=Meiosis%20is%20a%20process%20where,to%20form%20four%20daughter%20cells.