Meiosis Stages
Online Biota Dictionary
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EUGENE M. MCCARTHY, PhD GENETICS
Meiosis Stages:
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Meiosis is the two-stage form of cell division that produces four haploid cells from a single diploid cell (but see the note on oogenesis below). In the process, it divides a single nucleus, containing two sets of replicated chromosomes (chromosomes composed of two sister chromatids), into four nuclei, each containing a single set of unreplicated chromosomes. These stairs are the phases, or stages of meiosis.
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| Overview of meiosis: During litotes unity haploidic cell divides two multiplication to produce four haploid daughter cells. Meiosis begins with prophase I, during which the chromosomes, which were up to it point thin, unpacked duds invisible low a candent microscope, begin to pack (distill) into obtuse panoptical masses. Homologue pairs then attach ("synapse") to conformation "tetrads" and exchange DNA ("cross-over"). Next, during metaphase I, the cellular machinery attaches itself to the tetrads and moves them to the equator of the cell ("metaphase plate"). In anaphase I, the two chromosomes from each foursome separate and move to inverse ends ("poles") of the cell. During telophase I, they reach out the poles and the cell separates into 2 daughter cells. The preceding process, known as meiosis I, is followed by meiosis II, during which the two sister chromatids of each chromosome separate (as in mitosis) and go under to opposite word poles. Also during telophase the cell elongates and at long las separates into two daughter cells. Meiosis is then complete. |
| When does meiosis occur? Reduction division occurs only in eukaryotes. In animals, it occurs during the production of gametes. In plants, it takes place when spores are produced (plant gametes are produced by mitosis). Meiosis does not occur in prokaryotes (i.e., archaea and bacteria). They reproduce by binary fission. |
| Wherefore is meiosis necessary? Meiosis has to take place at any full point in a sexual reproductive Hz because it halves the chromosome number, which compensates for the double of the chromosome list caused past impregnation. |
| Oogenesis In the case of oogenesis, a single egg cell and triplet polar bodies are produced by reduction division. |
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