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Chromosome 21 from Human Genome Program Normal human Karyotype. 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 ...
Down syndrome (also known by the karyotype 47,XX,+21 for females and 47,XY,+21 for males) [99] is mostly caused by a failure of the 21st chromosome to separate during egg or sperm development, known as nondisjunction. [92] As a result, a sperm or egg cell is produced with an extra copy of chromosome 21; this cell thus has 24 chromosomes.
A karyotype of somebody affected with Down syndrome, depicting the presence of a full additional copy of chromosome 21. 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 ...
Trisomy 21, an extra copy of the 21st chromosome, is responsible for causing Down syndrome, and the mouse chromosome 16 closely resembles human chromosome 21. [1] In 1979, trisomy of the mouse chromosome 16 (Ts16) initially showed potential to be a model organism for human Down syndrome. [2]
The presence of an extra chromosome 21, which is found in Down syndrome, is called trisomy 21. Trisomy 18 and Trisomy 13, known as Edwards syndrome and Patau syndrome, respectively, are the two other autosomal trisomies recognized in live-born humans. Trisomy of the sex chromosomes is also possible, for example , , and . 4/5
Trisomies are sometimes characterised as "autosomal trisomies" (trisomies of the non-sex chromosomes) and "sex-chromosome trisomies." Autosomal trisomies are described by referencing the specific chromosome that has an extra copy. [citation needed] Thus, for example, the presence of an extra chromosome 21, which is found in Down syndrome, is ...
Trisomy 21 is a form of Down syndrome that occurs when there is an extra copy of chromosome 21. The result is a genetic condition in which a person has 47 chromosomes instead of the usual 46. During egg or sperm development the 21st chromosome does not separate during either the egg or sperm development. The result is a cell that has 24 ...
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". [7]