Question

on which chromosome does downs syndrome occur when theres extra dna? 24th chromosome 21st chromosome 23rd chromosome

Explanation:

Down's Syndrome (Trisomy 21) is caused by an extra copy of the 21st chromosome, resulting in three copies (trisomy) of chromosome 21 instead of the usual two. The 24th chromosome does not exist in the standard human karyotype, and the 23rd chromosome is related to sex determination (X and Y chromosomes), not Down's Syndrome.

Answer:

B. 21st chromosome