PATHOLOGY

Detailed explanation-1: -Trisomy 21 is the most common chromosomal anomaly in humans, affecting about 5, 000 babies born each year and more than 350, 000 people in the United States. Also known as Down syndrome, trisomy 21 is a genetic condition caused by an extra chromosome.

Detailed explanation-2: -Down syndrome is a condition in which a person has an extra chromosome. Chromosomes are small “packages” of genes in the body. They determine how a baby’s body forms and functions as it grows during pregnancy and after birth.

Detailed explanation-3: -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. Mosaic Down syndrome.

Detailed explanation-4: -Down syndrome (DS), also known as trisomy 21, is caused by the presence of all or part of a third copy of chromosome 21 (Figure 1a, b). It is named after John Langdon Down, the British physician who described the syndrome for the first time in 1866.