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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 ...
Partial monosomy can occur in unbalanced translocations or deletions, in which only a portion of the chromosome is present in a single copy (see deletion (genetics)). Monosomy of the sex chromosomes (45,X) causes Turner syndrome. 2: Disomy: Disomy is the presence of two copies of a chromosome.
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
Rather than having monosomy, or only one copy, the majority of aneuploid people have trisomy, or three copies of one chromosome. [ citation needed ] An example of trisomy in humans is Down syndrome , which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called "trisomy 21".
[1] [2] A majority of i(Xq) are created by U-type strand exchange. A breakage and reunion in the pericentric region of the p arm results in a dicentric isochromosome. [ 4 ] Some of the p arm can be found in this formation of i(Xq), but a majority of the genetic material on the p arm is lost so it is considered absent.
A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes.
The common autosomal trisomies (21, 18, 13) made up a smaller number of cases of mosaicism detected on CVS, but were more often confirmed in fetal tissue (19%). [3] On the other hand, the uncommon autosomal trisomies accounted for a greater number of placental mosaicism cases, but were less often confirmed in fetal tissue (3.2%). [ 3 ]
A contiguous gene syndrome (CGS), also known as a contiguous gene deletion syndrome, is a clinical phenotype caused by a chromosomal abnormality, such as a deletion or duplication that removes several genes lying in close proximity to one another on the chromosome. The combined phenotype of the patient is a combination of what is seen when any ...