"Cells and Cancer and Mitosis and Meiosis"Y

Mitosis is the type of cell division by which a single cell divides in such a way to provide two genetically identical "daughter cells". This is the method by which the body produces new cells for both growth and repair of aging or damaged tissues throughout the body. Meiosis (reduction division) is the form of cell division in which a cell divides into four "daughter cells" each of which has half of the number of chromosomes of the original cell. Meiosis occur prior to the formation of sperm (in males) and ova (in females); gametes.  

Mitosis and Meiosis both represent cell division that occur in humans and other animals. These cell division processes share many aspects, including the production of new cells and replication of genetic material. Both mitosis and meiosis are associated with cytokinesis. The end result of both are daughter cells produce from a parent cell. The fundamental sequence of events in mitosis is the same as in meiosis (in meiosis it happens twice.) Both processes include the breakdown of the nuclear membrane, the separation of genetic material into two groups, followed by cell division and the reformation of the nuclear membrane in each cells. The processes differ in two fundamental. Meiosis has two rounds of genetic separation and cellular division while mitosis only has one of each. In meiosis homologous chromosomes separate leading to daughter cells that are not generally identical. In mitosis the daughter cells are identical to the parent as well as to each other. Three benefits of genetic variation which results from meiosis are:

1. Crossing-over of homologous chromosomes (recombines the maternally- and paternally- derived chromosomes to create new allel combinations.)

2.Random segregation of homologous chromosomes ( the maternally- and paternally- derived chromosomes will go randomly into the two daughter cells during meiosis 1).

3. Random segregation of the sister chromatids during meiosis II and mitosis, sister chromatids are identical, but due to crossing-over, in meiosis, they're not, so random segregation of them is another way there's increased variation.

I think the crossing-over benefit is most significant because this creates genetic diversity by allowing genes from each parent to intermix, resulting in chromosomes with a different genetic complement. The exchange occurs bewteen non-sisters chromatids. Because genes often interact with each other, the new combination of genes on a chromosome can lead to new traits in offsprings.