The form of mental retardation that is caused by the presence of an extra chromosome is
A) phenylketonuria.
B) hydrocephaly.
C) psychosocial.
D) Down syndrome.

Question

Quizplus · Accepted Answer

Down syndrome is caused by the presence of an extra copy of chromosome 21 (trisomy 21). Phenylketonuria is a genetic disorder, but it is caused by mutations in a specific gene rather than an extra chromosome. Hydrocephaly is a condition in which there is an abnormal buildup of cerebrospinal fluid in the brain, but it is not necessarily related to genetic factors. Psychosocial factors refer to social and psychological influences on behavior and development, rather than genetic or physical causes of mental retardation.

The Form of Mental Retardation That Is Caused by the Presence