Meiosis!

Meiosis is defined as cell division in sexually reproducing organisms that reduces amount of genetic information by half.

Meiosis: There are two stages of meiosis that occur. In the first stage it starts out with a random alignment between the female chromosomes and the male chromosomes. In the anaphase stage, the sister chromatids, (two identical copies of a single chromosome connected by a centromere), stay together and the homologous chromosomes, (a pair of complete chromosomes), separate.

During meiosis one there is a crossing over, which is where the mother and father’s chromosomes are mixed creating a child’s DNA. (Ex. Blue eyes brown hair or brown eyes and blonde hair)

In the end of Meiosis one, chromosomes consist of two chromatids (one of two identical copies of DNA)

http://www.macroevolution.net/images/sister-chromatids-275.jpg

http://mrskingsbioweb.com/images/cell.h1.jpg

Meiosis two: There is no crossing over in Meiosis two. Meiosis two only happens when the egg is fertilized by sperm. In the end of Meiosis I there are two haploid cells, which by the end of meiosis two will be divided into four haploid cells. The four main steps as seen in this picture are prophase II, Metaphase II, Anaphase II, and Telophase II.

In prophase II there is a shortening and thickening of the chromatids. In metaphase II, the plate is rotated by 90 degrees so it is horizontal instead of perpendicular. In anaphase II, the sister chromatids are pulled apart. They are now referred to as sister chromosomes and move to opposite poles. Finally in telophase II, four daughter cells are produced, each having a haploid (contains one complete set of chromosomes) set of chromosomes. Meiosis is then complete.

http://www.biology.iupui.edu/biocourses/n100/images/meiosis2cropped.jpg