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Last Updated on April 6, 2023 by Shabnam Sengupta
Mosaic down syndrome is the rare form of down syndrome. In this, a person has only some cells with an extra copy of chromosome 21. Here, there are two cell lineages. One of them is with the normal number of chromosomes and the other one is with an extra number of chromosomes 21. The mechanism of occurrence consists of an error or misdivision after fertilisation during cell division. Genetic variation refers to the differences in DNA sequence among individuals of a species or population. This variation can occur due to several mechanisms, including mutation, recombination, and migration, among others. In this article, we will determine whether there are any genetic variations of down syndrome and what are they.
Are there any genetic variations of down syndrome?
Yes, there are three genetic variations of down syndrome. The presence of an extra copy of chromosome 21 causes down syndrome, and there are several ways that this can occur. Any of the three genetic variations can cause down syndrome, namely Trisomy 21, Mosaic Down syndrome, and Translocation Down syndrome.
Each of these variations can result in a slightly different presentation of Down syndrome, with varying degrees of severity and different associated health issues. However, all forms of down syndrome are caused by the presence of extra genetic material from chromosome 21.
What are the different types of genetic variations of down syndrome?
Trisomy 21 occurs about 95 percent of the time in cases of Down syndrome. In this variation, a person has three copies of chromosome 21, instead of the usual two copies, in all cells. It is caused by abnormal cell division during the development of the egg cell or sperm cell. Around 90% of free trisomy 21 is due to a maternal meiotic error, and only a small fraction is due to paternal errors.
Translocation down syndrome occurs when a portion of chromosome 21 becomes attached (translocated) to another chromosome before or at conception. These children have the usual two copies of chromosome 21, but they also have additional genetic material from chromosome 21 attached to another chromosome.
Mosaic down syndrome is a rare form of down syndrome in which a person has only some cells with an extra copy of chromosome 21. Here, there are two cell lineages, one with the normal number of chromosomes and another one with an extra number of chromosomes 21. The mechanism of occurrence consists of an error or mis division after fertilization during cell division.
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