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. [91] [96] 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.
Genetics of Down syndrome. Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on chromosome 21, either in whole ( trisomy 21) or part (such as due to translocations ). The effects of the extra copy varies greatly from individual to individual, depending on the extent of the extra copy ...
Trisomy. Example of trisomy 21 detected via qPCR short tandem repeat analysis. Specialty. Medical genetics. A trisomy is a type of polysomy in which there are three instances of a particular chromosome, instead of the normal two. [ 1] A trisomy is a type of aneuploidy (an abnormal number of chromosomes).
Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. [ 1][ 2] It does not include a difference of one or more complete sets of chromosomes. A cell with any number of complete chromosome sets is called a euploid cell.
Trisomy 21, one of the three types of Down syndrome, indicates that an individual has a duplicate of chromosome 21. The extra chromosome changes how one’s brain and body develop, and can lead to ...
The presence of this extra copy is also referred to as Trisomy 21. The following conditions are caused by changes in the structure or number of copies of chromosome 21: Cancers : Rearrangements ( translocations ) of genetic material between chromosome 21 and other chromosomes have been associated with several types of cancer.
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.).
Robertsonian translocation ( ROB) is a chromosomal abnormality where the entire long arms of two different chromosomes become fused to each other. It is the most common form of chromosomal translocation in humans, affecting 1 out of every 1,000 babies born. [ 1] It does not usually cause medical problems, though some people may produce gametes ...