NEET BIOLOGY

Detailed explanation-1: -A medical term for having an extra copy of a chromosome is ‘trisomy. ‘ Down syndrome is also referred to as Trisomy 21. This extra copy changes how the baby’s body and brain develop, which can cause both mental and physical challenges for the baby.

Detailed explanation-2: -Trisomy 21. 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-3: -The classic form is the most common chromosomal disorder, in which there is one extra X chromosome resulting in the karyotype of 47, XXY [18]. Double aneuploidy was first described in a patient with both Down and Klinefelter (48, XXY, +21) syndromes.

Detailed explanation-4: -Down syndrome is a condition or a syndrome, not a disease. People “have” Down syndrome, they do not “suffer from” it and are not “afflicted by” it. “Typically developing” or “typical” is preferred over “normal.”

Detailed explanation-5: -There are three types of Down syndrome: trisomy 21 (nondisjunction), translocation and mosaicism.