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Polyploidy is the result of whole-genome duplication during the evolution of species. It may occur due to abnormal cell division, either during mitosis, or more commonly from the failure of chromosomes to separate during meiosis or from the fertilization of an egg by more than one sperm. [1]
[23] [24] Many bodily processes can be affected due to the hereditary nature of this disease; if the disease is present in the DNA of both the sperm and the egg, then it will be present in essentially every cell and organ in the body; these mutations can occur initially in the germline cells, or be present in all parental cells. [23]
Haploid cells may divide again (by mitosis) to form more haploid cells, as in many yeasts, but the haploid phase is not the predominant life cycle phase. In most diplonts, mitosis occurs only in the diploid phase, i.e. gametes usually form quickly and fuse to produce diploid zygotes. [14]
A specialized type of cell division that occurs exclusively in sexually reproducing eukaryotes, during which DNA replication is followed by two consecutive rounds of division to ultimately produce four genetically unique haploid daughter cells, each with half the number of chromosomes as the original diploid parent cell. Meiosis only occurs in ...
In biology, evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how evolution occurs. Biological populations evolve through genetic changes that correspond to changes in the organisms ' observable traits .
This occurs as sexual reproduction involves the fusion of two haploid gametes (the egg and sperm) to produce a zygote and a new organism, in which every cell has two sets of chromosomes (diploid). During gametogenesis the normal complement of 46 chromosomes needs to be halved to 23 to ensure that the resulting haploid gamete can join with ...
Somatic mosaicism (also known as clonal mosaicism) occurs when the somatic cells of the body are of more than one genotype. In the more common mosaics, different genotypes arise from a single fertilized egg cell, due to mitotic errors at first or later cleavages.
When a nucleus is added to an egg during somatic cell nuclear transfer, the egg starts dividing in minutes, as compared to the days or months it takes for reprogramming during embryonic development. If time is the responsible factor, it may be possible to delay cell division in clones, giving time for proper reprogramming to occur. [citation ...