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Turner syndrome is the only full monosomy that is seen in humans — all other cases of full monosomy are lethal and the individual will not survive development. Cri du chat syndrome – (French for "cry of the cat" after the persons' malformed larynx) a partial monosomy caused by a deletion of the end of the short arm of chromosome 5
The terms "partial monosomy" and "partial trisomy" are used to describe an imbalance of genetic material caused by loss or gain of part of a chromosome. In particular, these terms would be used in the situation of an unbalanced translocation , where an individual carries a derivative chromosome formed through the breakage and fusion of two ...
The following is a partial list of genes on human chromosome 21. For complete list, see the link in the infobox at the top of the article. ... (partial monosomy 21 ...
2p15-16.1 microdeletion is an extremely rare genetic disorder caused by a small deletion in the short arm of human chromosome 2. First described in two patients in 2007, [1] by 2013 only 21 [citation needed] people have been reported as having the disorder in the medical literature. [2] [3] [4] [5]
A karyotype of an individual with trisomy 21, showing three copies of chromosome 21. An abnormal number of chromosomes is known as aneuploidy, and occurs when an individual is either missing a chromosome from a pair (resulting in monosomy) or has more than two chromosomes of a pair (trisomy, tetrasomy, etc.).
An anaphase lag of a chromosome 21 in a Down syndrome embryo leads to a fraction of euploid cells (2n cells), phenomenon described as "aneuploidy rescue". There is considerable variability in the fraction of cells with trisomy 21, both as a whole and tissue-by-tissue. This is the cause of 1–2% of the observed Down syndromes. [4]
In rare cases this translocation results in Down syndrome and Patau syndrome. [2] Robertsonian translocations result in a reduction in the number of chromosomes. A Robertsonian evolutionary fusion, which may have occurred in the common ancestor of humans and other great apes, is the reason humans have 46 chromosomes while all other primates ...
A common example is Down syndrome, which is caused by possessing three copies of chromosome 21 instead of the usual two. [9] Partial aneuploidy can also occur as a result of unbalanced translocations during meiosis. [11] Deletions of part of a chromosome cause partial monosomies, while duplications can cause partial trisomies.