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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 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 ...
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 ...
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.
MDS is a contiguous gene syndrome – a disorder due to the deletion of multiple gene loci adjacent to one another. The disorder arises from the deletion of part of the small arm of chromosome 17p (which includes both the LIS1 and 14-3-3 epsilon genes), leading to partial monosomy.