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  2. Down syndrome - Wikipedia

    en.wikipedia.org/wiki/Down_syndrome

    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.

  3. Genetics of Down syndrome - Wikipedia

    en.wikipedia.org/wiki/Genetics_of_Down_syndrome

    The trisomy 21 karyotype figure shows the chromosomal arrangement, with the prominent extra chromosome 21. Trisomy 21 is the cause of approximately 95% of observed Down syndrome, with 88% coming from nondisjunction in the maternal gamete and 8% coming from nondisjunction in the paternal gamete. [ 4 ]

  4. Chromosome 21 - Wikipedia

    en.wikipedia.org/wiki/Chromosome_21

    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:

  5. Aneuploidy - Wikipedia

    en.wikipedia.org/wiki/Aneuploidy

    Trisomy refers to the presence of three copies, instead of the normal two, of a particular chromosome. 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 ...

  6. Trisomy - Wikipedia

    en.wikipedia.org/wiki/Trisomy

    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).

  7. Nondisjunction - Wikipedia

    en.wikipedia.org/wiki/Nondisjunction

    Note that chromosome 21 is present in 3 copies, while all other chromosomes show the normal diploid state with 2 copies. Most cases of trisomy of chromosome 21 are caused by a nondisjunction event during meiosis I (see text). Down syndrome, a trisomy of chromosome 21, is the most common anomaly of chromosome number in humans. [2]

  8. Transient myeloproliferative disease - Wikipedia

    en.wikipedia.org/wiki/Transient...

    Down syndrome is caused be the presence of an extra chromosome 21 (i.e. trisomy 21) due to a failure in normal chromosomal pairing or premature unpairing during the cell division of meiosis in egg or sperm cells. In these cases, virtually all cells in Down syndrome individuals bear an extra chromosome 21.

  9. A mom of 3 learned she had mosaic Down syndrome through ... - AOL

    www.aol.com/lifestyle/mom-3-learned-she-had...

    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 ...