Meiosis Comparison essays

Meiosis Comparison essays The two different types of meiosis, meiosis I and meiosis II, undergo the same interphase. In this phase, the chromosomes replicate like they do in the S-phase preceding mitosis. In prophase I, the homogonous chromosomes, or two sister chromosomes, come together and condense in a process called synapsis. The four chromatids of the pair of homogonous chromosomes visible under a microscope is called a tetrad. Some of these chromosomes crisscross at the chiasmata, a site where genetic material is exchanged, which help hold the chromosomes together. The genetic traits of the pair of chromosomes are then mixed homogeneously in a process called crossing over. Meanwhile, spindle fibers made of microtubules form as the centrosomes begin to separate to opposite poles of the cell. In Metaphase I, the chromosomes, now connected to kinetochore microtubules, line up in the metphase plate. The spindle fibers pull the chromosomes apart toward opposite ends in Anaphase I, but unlike Anaphase in mitosis, the chromosomes retain their centromeres. In telophaseI and cytokinesis, the chromosomes are completely relocated and at opposite ends of the cell. Each pole has a haploid chromosome, or a cell with a single set of chromosomes. Cytokinesis usually occurs simultaneously with telophase I. A pinch forms outside the cell, forming a cleavage furrow, and ultimately splitting the cell into two. In some cells, however, the chromosomes recondense in Interphase II before entering meiosis II. In meiosis II, each of the daughter cells of meiosis I undergo their own meiosis. In prophase II, the spindle apparatus forms. In metaphase II, the chromosomes line up just like they do in other variants of the metaphase. They separate and move toward opposite ends of the cell in anaphase II. In telophase II and cytokinesis, the cells divide by way of a cleavage furrow and create four daughter cells. Meiosis in animals occurs only in the ovaries and te...