how does the process of crossing over results in genetic variability in an organism due to meiotic cell division?
crossing over is when the homologous chromosomes pair up on the metaphase plate during meiosis 1, the homologous chromosomes swap short bits of dna. This is one of the sources of genetic variation in the offspring and one of the principle mechanisms of evolution. In more simple terms; the an individual inherits homologous chromosomes from their parents, except if the species is one like humans in which there is an xy difference on the sex chromosomes. During meiosis these chromosomes are duplicated and line up next to each other in the middle of the dividing reproductive cell (thats important, this only happens in reproductive cells! somatic cells (all the others) go through mitosis) After crossing over, they are pulled apart into two intermediary cells in which each has a duplicate set of chromosomes. These are called sister chromatids. They line up on the metaphase plate (the equator of the cell) of meiosis 2 just like what happened during meiosis 1. The sister chromatids are split apart and pulled to the two poles of the cell, which divides again, resulting in a total of 4 reproductive cells, each containing a half chromosome count of what the somatic cells all have. When two organisms reproduce, their reproductive cells fuse forming an embryo, which brings the chromosome count back to full. Once the organism has reached sexual maturity this process is repeated, producing new chromosomes that are different from the ones passed on from their parents. The source of this variation is the crossing over on metaphase plate 1 and the random assortment of the sister chromatids on metaphase plate 2. Hope this was helpful.
crossing over is when the homologous chromosomes pair up on the metaphase plate during meiosis 1, the homologous chromosomes swap short bits of dna. This is one of the sources of genetic variation in the offspring and one of the principle mechanisms of evolution. In more simple terms; the an individual inherits homologous chromosomes from their parents, except if the species is one like humans in which there is an xy difference on the sex chromosomes. During meiosis these chromosomes are duplicated and line up next to each other in the middle of the dividing reproductive cell (thats important, this only happens in reproductive cells! somatic cells (all the others) go through mitosis) After crossing over, they are pulled apart into two intermediary cells in which each has a duplicate set of chromosomes. These are called sister chromatids. They line up on the metaphase plate (the equator of the cell) of meiosis 2 just like what happened during meiosis 1. The sister chromatids are split apart and pulled to the two poles of the cell, which divides again, resulting in a total of 4 reproductive cells, each containing a half chromosome count of what the somatic cells all have. When two organisms reproduce, their reproductive cells fuse forming an embryo, which brings the chromosome count back to full. Once the organism has reached sexual maturity this process is repeated, producing new chromosomes that are different from the ones passed on from their parents. The source of this variation is the crossing over on metaphase plate 1 and the random assortment of the sister chromatids on metaphase plate 2. Hope this was helpful.
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