NEET BIOLOGY

Detailed explanation-1: -About 95 percent of the time, Down syndrome is caused by trisomy 21-the person has three copies of chromosome 21, instead of the usual two copies, in all cells. This is caused by abnormal cell division during the development of the sperm cell or the egg cell.

Detailed explanation-2: -Types of Down Syndrome Trisomy 21: About 95% of people with Down syndrome have Trisomy 21. With this type of Down syndrome, each cell in the body has 3 separate copies of chromosome 21 instead of the usual 2 copies.

Detailed explanation-3: -3q29 microdeletion syndrome is a condition that results from the deletion of a small piece of chromosome 3 in each cell. Features associated with the deletion vary widely but can include delayed development, intellectual disability, behavioral and psychiatric disorders, and physical abnormalities.

Detailed explanation-4: -Trisomy (’three bodies’) means the affected person has three copies of one of the chromosomes instead of two. This means they have 47 chromosomes instead of 46. Down syndrome, Edward syndrome and Patau syndrome are the most common forms of trisomy.

Detailed explanation-5: -A common form of aneuploidy is trisomy, or the presence of an extra chromosome in cells. “Tri-” is Greek for “three"; people with trisomy have three copies of a particular chromosome in cells instead of the normal two copies. Down syndrome (also known as trisomy 21) is an example of a condition caused by trisomy .