What are the genetics of Trisomy 21? (autosomal, sex-linked, recessive, dominant, etc)?

is it autosomal, sex-linked, recessive, dominant, etc? or is it non-disjunction. im confused about it all. .

What are the genetics of Trisomy 21? (autosomal, sex-linked, recessive, dominant, etc)?
What are the genetic changes related to Down syndrome?





Down syndrome is related to chromosome 21.





Most cases of Down syndrome result from trisomy 21, which means each cell in the body has three copies of chromosome 21 instead of the usual two copies. The extra genetic material disrupts the normal course of development, causing the characteristic features of Down syndrome. Although the connection between Down syndrome and Alzheimer disease is unclear, researchers believe that an extra copy of a particular gene on chromosome 21, the APP gene, may account for the increased risk.





A small percentage of Down syndrome cases occur when only some of the body's cells have an extra copy of chromosome 21. These cases are called mosaic Down syndrome.





Although uncommon, Down syndrome also can occur when part of chromosome 21 becomes attached (translocated) to another chromosome before or at conception. Affected people have two copies of chromosome 21, plus extra material from chromosome 21 attached to another chromosome. These cases are called translocation Down syndrome.





Can Down syndrome be inherited?


Most cases of Down syndrome are not inherited, but occur as random events during the formation of reproductive cells (eggs and sperm). An error in cell division called nondisjunction results in reproductive cells with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 21. If one of these atypical reproductive cells contributes to the genetic makeup of a child, the child will have an extra chromosome 21 in each of the body’s cells.





Mosaic Down syndrome is also not inherited. It occurs as a random error during cell division early in fetal development. As a result, some of the body’s cells have the usual two copies of chromosome 21, and other cells have three copies of the chromosome.





Translocation Down syndrome can be inherited. An unaffected person can carry a rearrangement of genetic material between chromosome 21 and another chromosome. This rearrangement is called a balanced translocation because there is no extra material from chromosome 21. Although they do not have signs of Down syndrome, people who carry this type of balanced translocation are at an increased risk of having children with the condition.





Hope that may help you!


Good luck!