Meiosis: What They Do

meisosis

the special type of cell division that results in cells with half the normal number of chromosomes

Chromosomes

threadlike structures made of DNA molecules that contain the genes

Prophase I (Meiosis)

homologous chromosomes pair up and form tetrads, crossing over occurs

Metaphase I (Meiosis)

Pairs of homologous chromosomes move to the equator of the cell.

Anaphase I (Meiosis)

Tetrads split up and head to opposite poles

Telophase I (Meiosis)

Cytokinesis occurs, the result are two haploid daughter cells

Prophase II (Stage 6)

chromosomes condense - nuclear membranes start to dissolve again. Sister chromatids are again joined by a centromere. Spindles start to reform between centrosomes.

Metaphase II (Stage 7)

Spindles are fully formed again and attach to the centromeres. The chromosomes line up down the middle of the spindles.

Anaphase II (Stage 8)

The spindles pull the sister chromatids apart. Each goes towards a different pole.

Telophase II (Stage 9)

Nuclear membranes start to form around the chromosomes again. A cleavage forms. Cytokinesis occurs and the two diploid cells have now divided into 4 haploid cells. In males this equals 4 sperm. In females this creates 1 egg and 3 polar bodies which are useless in humans.