What type of cell division is required for the formation of gametes?
Posted March 15, 2023
Meiosis is required for the formation of gametes. Meiosis is the process of a single cell dividing twice to create four haploid daughter cells containing half the amount of original DNA. These are known as gametes or sex cells. Meiosis has a total of nine stages which are divided between meiosis I and meiosis II. In meiosis I, interphase is the first step of cell division. During interphase, the DNA in the cell is copied creating two identical sets of chromosomes. Two centrosomes exist outside the nucleus, and microtubules extend from those centrosomes during interphase. The next step is prophase I, in which chromosomes join so that both copies of chromosome 1,2,3, etc, are together. Recombination and crossing over then occurs during this step, and at the end of prophase I the membrane dissipates around the nucleus, releasing chromosomes. The meiotic spindle then extends across the cell between the centrioles. The next step is metaphase I, in which the chromosome pairs line up adjacent to each other at the center of the cell. The centrioles are at opposite poles of the cell and the meiotic spindle fibers attach to one chromosome of each pair. Next, during anaphase I, the pair of chromosomes are separated by the meiotic spindle, pulling each chromosome to opposite poles of the cell (sister chromatids stay joined). Next, during telophase I each set of chromosomes gather together at each pole and a membrane is formed around each set creating two nuclei. Then, the single cell cleaves in the middle to form 2 separate daughter cells with a full set of chromosomes. This is known as cytokinesis.
During meiosis II, prophase II is the first step and the membrane around the nucleus in each daughter cell dissipates. The centrioles duplicate and once again the meiotic spindle forms. The next step is metaphase II, in which the two daughter cells line up adjacently at the center of the cell; the meiotic spindle fibers at each pole attach to each sister chromatid. Anaphase II is the next step, and the sister chromatids are pulled to opposite poles, and become separate chromosomes. Next, in telophase II, each set of chromosomes gather together at each pole and a membrane is formed around each set creating two nuclei. Cytokinesis then occurs again, and there are now a total of 4 haploid daughter cells each containing half a set of chromosomes.