![]() During synapsis, homologous chromosomes exchange genetic material between one another. Chromosomes may become coiled around each other and their chromatids may remain in contact at points called chiasmata. As prophase progresses, homologous chromosomes lie side by side and become intertwined rather like a zipper forming pairs called bivalents in a process called synapsis. This stage is manifested by the chromosomes becoming visible as distinct bodies as they get shorter and thicker and centrioles become arranged at opposite sides of the nucleus. There is also a build up of energy to be used up in the meiotic process. Another important process that takes place is the formation of new cellular organelles. The chromosomes are not visible as discrete structures but instead, they appear as a diffuse tangle of threads called chromatin. One of the most important processes in this stage is chromosomal replication in which each chromosome produces an exact copy or replica of itself. Here are list of stages of meiosis 1 and meiosis 2 as below:ĭiscover What Occurs During the Meiosis Stages Meiosis 1 Phases ![]() Each stage is followed by 1 or 2 indicating whether it belongs to meiosis 1 or 2. Each of the two meiotic divisions is divided into interphase, prophase, metaphase, anaphase and telophase. Meiosis 2 results in separation the sister chromatids and for this reason, it is known as equatorial division. In meiosis 1, the number of chromosomes is reduced by one-half and for this reason, it is called reduction division. It consists of two successive divisions which are meiosis 1 and meiosis 2. Although there is only one chromosome set, each homolog still consists of two sister chromatids.Meiosis is the type of cell division that is seen during the formation of gametes (sex cells). Therefore, only one full set of the chromosomes is present. The cells are haploid because at each pole there is just one of each pair of the homologous chromosomes. Two haploid cells are the end result of the first meiotic division. This cell plate will ultimately lead to the formation of cell walls that separate the two daughter cells. In plants, a cell plate is formed during cell cytokinesis by Golgi vesicles fusing at the metaphase plate. In nearly all species of animals and some fungi, cytokinesis separates the cell contents via a cleavage furrow (constriction of the actin ring that leads to cytoplasmic division). Then cytokinesis, the physical separation of the cytoplasmic components into two daughter cells, occurs without reformation of the nuclei. In some organisms, the chromosomes decondense and nuclear envelopes form around the chromatids in telophase I. In telophase I, the separated chromosomes arrive at opposite poles. With n = 23 in human cells, there are over 8 million possible combinations of paternal and maternal chromosomes. In this example, there are four possible genetic combinations for the gametes. The total possible number of different gametes is 2n, where n equals the number of chromosomes in a set. In this case, there are two possible arrangements at the equatorial plane in metaphase I. \( \newcommand\): Meiosis I ensures unique gametes: Random, independent assortment during metaphase I can be demonstrated by considering a cell with a set of two chromosomes (n = 2).
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