Mechanism of cell division including mitosis and meiosis
Answers
Answer:
Body cells of all animals and plants undergo a cell division called mitosis.
The germinal epithelial cells of animals undergo a cell division called meiosis
Explanation:
Mitosis
Mitosis is a continuum of changes but biologists like break down the stages of mitosis into four main stages, prophase, metaphase, anaphase and telophase.
The focus in this class is on an understanding of the process and not memorization of phases.
The only phase name you will need to remember is metaphase.
In mitosis the nuclear membrane is broken down, spindle fibres (microtubules) attach to the chromatids at the centromere and pull apart the chromatids.
When the chromatids reach separate ends of the cells the spindle fibres disintegrate and a nuclear membrane rebuilds around the chromosomes making two nuclei.
Each nucleus is identical to the original nucleus as it was in G1.
Meiosis
Meiosis is the form of nuclear cell division that results in daughter cells that have one half the chromosome numbers as the original cell.
In organisms that are diploid, the end result is cells that are haploid. Each daughter cell gets one complete set of chromosomes, i.e., one of each homologous pair of chromosomes.
In humans, this means the chromosome number is reduced from 46 to 23.
The only cells that undergo meiosis will become sperm or eggs.
The joining together of a sperm and egg during fertilization returns the number of the chromosomes to 46.
Cells that undergo meiosis go through the cell cycle including the S phase so begin the process with chromosomes that consist of two chromatids just as in mitosis.
Meiosis consists of meiosis I and meiosis II. In meiosis I homologous chromosomes are separated into different nuclei.
This is the reduction division; chromosome number is cut in half. Meiosis II is very similar to mitosis, chromatids are separated into separate nuclei.
As in mitosis, it is spindle fibres that “pull” the chromosomes and chromatids apart.
The end result of meiosis is four cells, each with one complete set of chromosomes instead of two sets of chromosomes.