Search results
Results from the WOW.Com Content Network
The extra chromosome content can arise through several different ways. The most common cause (about 92–95% of cases) is a complete extra copy of chromosome 21, resulting in trisomy 21. [92] [97] In 1–2.5% of cases, some of the cells in the body are normal and others have trisomy 21, known as mosaic Down syndrome.
This method can diagnose PKS in 10 week and older fetuses. In cfDNA screening, DNA from a mothers blood is extracted and screened for the presence of specific chromosome abnormalities such as those associated with the Down syndrome, Patau syndrome (also termed trisomy 13 [8]), and Edwards syndrome (also termed trisomy 18 [9]).
Karyotype of a human with Trisomy 21 (Down syndrome). Trisomies can occur with any chromosome, but often result in miscarriage rather than live birth.For example, Trisomy 16 is most common in human pregnancies, occurring in more than 1%, but the only surviving embryos are those having some normal cells in addition to the trisomic cells (mosaic trisomy 16). [3]
In about 1 to 2% of persons of Down syndrome, mosaicism is seen — that is when some of the cells have 46 chromosomes (two No. 21 chromosomes) and some cells have 47 chromosomes (three No. 21 ...
The clinical name for Down syndrome is trisomy 21, a condition in which a person is born with an extra chromosome, causing mild to moderate cognitive disability, developmental delays and physical ...
In unbalanced forms, Robertsonian translocations cause chromosomal deletions or addition and result in syndromes of multiple malformations, including trisomy 13 (Patau syndrome) and trisomy 21 (Down syndrome). The most frequent forms of Robertsonian translocations are between chromosomes 13 and 14, 14 and 21, and 14 and 15. [2]
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 ]
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. Most embryos with triploidy miscarry early in development.