Down syndrome can result from
A) three copies of chromosome 21.
B) a translocation of a part of chromosome 21.
C) a reciprocal translocation between any two autosomes.
D) both A and B

Question

Quizplus · Accepted Answer

Down syndrome, also known as trisomy 21, is caused by a person having three copies (instead of two) of chromosome 21. This can result from either an error in cell division during the formation of the egg or sperm, or from a translocation of a part of chromosome 21 to another chromosome. Therefore, both choices A and B can result in Down syndrome. Choice C, a reciprocal translocation between any two autosomes, would not result in Down syndrome unless chromosome 21 is involved in the translocation.

Down Syndrome Can Result from