Cell Division 批評

Two cells undergo:

Prophase II 

Metaphase II

Anaphase II - pairs of sister chromatids are separated, each new daughter cell inherits one chromatid from each chromosomes. Four, genetically different, haploid daughter cells are produced (gametes) 

Telophase II

(All are similar to Mitosis)

It is needed for growth and repairing tissue damage. It has 4 stages:

Prophase - Chromosomes condense (get shorter and fatter) Centrioles move to opposite ends of cells, forming the spindle. The nuclear envelope breaks down.

Metaphase - Chromosomes line up in equator and become attach to the spindle by their centromere. 

Anaphase - Centromeres divide, separating each pair of chromatids. Spindle contracts, pulling chromatids to opposite ends of the cells, centromeres first. 

Telophase - Chromatids uncoil. Nuclear envelope forms around each group of chromosomes, there are now two nuclei. 

Meiosis involves 2 divisions. Meiosis I halves the chromosome numbers. 

Prophase I - Chromosomes condense, shorter and fatter. They arrange themselves in homologous pairs and crossing-over occurs. (Similarly to Mitosis, Centrioles move to opposite ends, forming spindle, nuclear envelope breaks down)

Metaphase I - Homologous pair line up across equator, they attach to spindle by their centromeres

Anaphase I - Spindle contracts, separating homologous pairs, one chromosomes goes to each end of the cell

Telophase I - nuclear envlope forms around each group of chromosomes

Cytokinesis - Division of the cytoplasm occurs and two haploid cells are produced