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

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Down syndrome is caused by an extra copy of the 21st chromosome, resulting in a total of three copies instead of the usual two. This genetic abnormality occurs randomly during fetal development and is the most common chromosomal disorder.

What Is the Cause of Down Syndrome