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Polyploidy occurs in some tissues of animals that are otherwise diploid, such as human muscle tissues. [45] This is known as endopolyploidy . Species whose cells do not have nuclei, that is, prokaryotes , may be polyploid, as seen in the large bacterium Epulopiscium fishelsoni . [ 46 ]
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
Triploid syndrome, also called triploidy, is a chromosomal disorder in which a fetus has three copies of every chromosome instead of the normal two. If this occurs in only some cells, it is called mosaic triploidy and is less severe.
The extreme in polyploidy occurs in the fern genus Ophioglossum, the adder's-tongues, in which polyploidy results in chromosome counts in the hundreds, or, in at least one case, well over one thousand. [citation needed] It is possible for polyploid organisms to revert to lower ploidy by haploidisation. [citation needed]
Polyploidy, or whole genome duplication is a product of nondisjunction during meiosis which results in additional copies of the entire genome. Polyploidy is common in plants, but it has also occurred in animals, with two rounds of whole genome duplication in the vertebrate lineage leading to humans. [4]
The cell eventually reaches megakaryocyte stage and loses its ability to divide. However, it is still able to replicate its DNA and continue development, becoming polyploid. [4] The cytoplasm continues to expand and the DNA amount can increase up to 64n in humans and 256n in mice.
In polyploid obligate parthenogens, like the whiptail lizard, all the offspring are female. [ 29 ] In many hymenopteran insects such as honeybees, female eggs are produced sexually, using sperm from a drone father, while the production of further drones (males) depends on the queen (and occasionally workers) producing unfertilized eggs.
American Journal of Human Genetics. 63 (6): 1912– 4. doi:10.1086/302149. PMC 1377663. PMID 9837845. Van Opstal D, Van den Berg C, Deelen WH, et al. (January 1998). "Prospective prenatal investigations on potential uniparental disomy in cases of confined placental trisomy". Prenatal Diagnosis. 18 (1): 35– 44.