What chromosomal abnormality is linked to Down Syndrome?

Down Syndrome is primarily caused by the presence of an extra copy of the 21st chromosome, leading to a total of three copies instead of the usual two. This condition is scientifically known as Trisomy 21. The additional genetic material affects typical development and can result in the characteristic features and developmental delays associated with Down Syndrome.

The other chromosomal abnormalities listed do not correlate with Down Syndrome. For instance, a missing part of chromosome 5 is associated with Cri du Chat syndrome, while deletions on chromosome 15 can relate to conditions like Prader-Willi syndrome and Angelman syndrome. Mutations on the Y chromosome typically involve sex determination and might affect male characteristics but are not linked to Down Syndrome. Therefore, the extra copy of the 21st chromosome is specifically tied to the genetic basis of Down Syndrome.