Down syndrome is caused by the presence of an extra chromosome 21, resulting in three copies of this chromosome instead of the usual two. This is known as trisomy 21 and is usually the result of a genetic accident during the formation of the egg or sperm. It is not caused by a single abnormal dominant gene, lack of acetylcholine, toxic psychosis or toxic dementia.

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Down Syndrome Is

Question 50

Multiple Choice

Down syndrome is

A) a toxic psychosis.
B) a toxic dementia.
C) the result of a single abnormal dominant gene.
D) associated with a lack of acetylcholine.
E) the result an extra chromosome 21 resulting from a genetic accident.

Correct Answer: