Figure 20.2 Mitosis and Meiosis Animation Video
Transcript:
Mitosis and Meiosis
Mitosis and meiosis are two different types of cell division. Before either process can begin, chromosomes in the mother cell must duplicate. In mitosis, cells copy their genetic material and then split into two identical cells.
As mitosis begins, the duplicated chromosomes become attached at a point called the centromere and form pairs. Once attached, the chromosomes line up in the middle of the cell. A special protein splits the pairs in half and the chromosomes are pulled to opposite sides of the cell.
Eventually, the cell itself divides into two identical cells, which are called the daughter cells of mitosis. Mitosis occurs in cells throughout the body.
Unlike mitosis, meiosis occurs only in the testes and ovaries. Meiosis is a process by which cells halve their genetic material, creating either sperm or ova that have only half the number of chromosomes found in other cells.
During the first phase of meiosis, pairs of duplicated chromosomes attach at the centromere. Then, each chromosome pair attaches with another to form clusters of four chromosomes. The formation of these clusters allows chromosomes to form connections called crossovers. Portions of the chromosomes become swapped when these crossovers occur.
During the first cell division in meiosis, the clusters of four separate and the cell splits. Each daughter cell contains paired chromosomes. These daughter cells then split again, as part of a process called meiosis two. This time, the chromosome pairs are separated. The final division creates four new daughter cells.