cell division:meiosi

CELL DIVISION: MEIOSIS

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cell division:meiosis

Meiosis gives space for genetic recombination. It is the reason why siblings having the same parent look differently from each other and their parents. This is the type of cell division occurring in higher organisms such as ape, birds, cat and man.

Not to be confused with mitosis

Meiosis contributes to genetic variation. Meiosis, unlike mitosis, does not occur in the body cells. It  occur in sperm and egg cells instead.

Humans have 46 chromosomes in their body cells. The gamete cells, on the other hand, possess 23 chromosomes. However, there exists a difference between mitotic and meiotic cell division, in that mitosis results in two (2) diploid daughter cell while meiosis results in haploid (4) cells. Meiosis is also known as reductional division.

A major similarity is the preceding stage for both meiosis and mitosis is known as interphase.

The interphase is divided into three phases:

G1-phase is the phase of growth and synthesis while S-phase is also called the phase of DNA synthesis or replication. G2-phase is the final phase of meiotic cell division

However, meiosis occurs in the following phases:

  • Karyokinesis I
  • Cytokinesis I
  • Karyokinesis II
  • Cytokinesis II

Karyokinesis is known as the division of the nucleus while cytokinesis, on the other hand, is known as the division of the cytoplasm.

Karyokinesis I is divided into

  1. Prophase I
  2. Metaphase I
  3. Anaphase I
  4. Telophase I

Prophase I

The chromosome becomes visible while the nuclear envelope disappears. Homologous chromosomes in the cells crossover, thus, leading to exchange of segment. This is particularly responsible for the difference between offspring having the same parent.

Prophase

Metaphase I

At this phase, the chromosomes assemble at the spindle fibre in homologous pair and moves towards the center of the spindle fibre.

Anaphase I

Sister Chromatids divide so that there are an equal amount of chromosomes on either side of the cell and moves towards the centriole.

Telophase I

The chromosomes completely reach the pole at each end, this is followed by cytokinesis and karyokinesis II.

KARYOKINESIS II is also divided into

Prophase II

The chromosomes in the cells from the first mitotic division becomes visible, the nuclear membrane disappears while the centriole forms on the spindle fibre.

Metaphase II

The chromosomes line up along the middle line on the spindle fibre.

Anaphase II

The chromatid splits into two and moves along the spindle fibre towards the centriole.

Telophase II

At this stage, the chromosome reaches the end of the centriole followed by cytokinesis II, thus giving rise to four distinct gamete cells with 23 chromosomes each.

Cite this article as: Fagbohun, S.O., "CELL DIVISION: MEIOSIS," in ATG Ventures, 04/01/2019, https://atgventure.com/cell-division-meiosis/.

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