What is the cause of Down syndrome?

A) an extra chromosome on the 21^st pair
B) an extra X chromosome on the 23^rd pair
C) neurotransmitter excesses
D) neurotransmitter deficiencies

Down Syndrome

A genetic disorder caused by the presence of all or part of a third copy of chromosome 21, characterized by physical growth delays, characteristic facial features, and often intellectual disability.

Extra Chromosome

The presence of an additional chromosome in an individual's genetic makeup, which can result in developmental disorders such as Down syndrome.

21st Pair

Refers to the 21st pair of chromosomes in humans, which is critical for determining genetic conditions such as Down syndrome.