AP BIOLOGY

Detailed explanation-1: -In most cases of Down syndrome, a child gets an extra chromosome 21-for a total of 47 chromosomes instead of 46. Rarely, the extra chromosome 21 attaches to another chromosome. This extra genetic material causes the physical features and developmental delays in people with Down syndrome.

Detailed explanation-2: -Down syndrome (also known as trisomy 21) is an example of a condition caused by trisomy . People with Down syndrome typically have three copies of chromosome 21 in each cell, for a total of 47 chromosomes per cell. Monosomy, or the loss of one chromosome in cells, is another kind of aneuploidy.

Detailed explanation-3: -Typically, a baby is born with 46 chromosomes. Babies with Down syndrome have an extra copy of one of these chromosomes, chromosome 21. A medical term for having an extra copy of a chromosome is ‘trisomy.’ Down syndrome is also referred to as Trisomy 21.

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: -Triple X syndrome is also called 47, XXX syndrome because the extra X chromosome results in 47 chromosomes in each cell instead of the usual 46.