Which statement accurately describes Down syndrome?

• A. Down syndrome results from a deletion on chromosome 15.
• B. Down syndrome is characterized by an extra Y chromosome.
• C. Down syndrome is caused by an extra copy of chromosome 21.
• D. Down syndrome is a result of a single gene mutation.

Answer: (C)

Verified step by step guidance

1. Understand that Down syndrome is a genetic disorder caused by chromosomal abnormalities.
2. Recall that Down syndrome is specifically associated with an extra chromosome, not a deletion or a single gene mutation.
3. Identify that Down syndrome is characterized by the presence of an extra copy of chromosome 21, a condition known as trisomy 21.
4. Eliminate options that mention deletions or mutations on other chromosomes, as these do not describe Down syndrome.
5. Conclude that the statement 'Down syndrome is caused by an extra copy of chromosome 21' accurately describes the condition.