Science - Module 5

Mitosis and meiosis are the two ways theat cells reproduce.

MITOSIS

In mitosis a cell divides to produce two cells with identical sets of chromosomes. this happens in order to produce new cells for GROWTH and REPAIR or REPLACEMENT of tissues.

Parental cell with 2 pairs of chromosomes --> Each chromosome replicates itself. --> The replicas now seperate from the originals and the cell divides for the only time. --> Each "daughter" cell has the same number of chromosomes as the parental cells, and contains the same genes as the parental cell.

MEIOSIS

In meiosis a DIPLOID cell divides twice to produce four HAPLOID cells with genetically different sets of chromosomes. This happens in sexually reproducing organisms to produce GAMETES.

A diploid* cell with pairs of chromosomes. --> Each chromosomes replicates itself. --> Chromosomes part company and move to opposite sides with their replicas. --> Cell divides for the first time. --> Replicas now seperate and the second cell division takes place. --> Four haploid** gametes, each with half the number of chromosomes as the parental cell.

*A diploid cell is a cell that contains two sets of chromosomes. One set of chromosomes is donated from each parent.

**A haploid cell is a cell that contains one complete set of chromosomes. Gametes are haploid cells that are produced by meiosis.