Question

A man with trisomy 21 could pass Down syndrome to offspring if he

A. produces sperm that have two copies of chromosome 21.
B. produces sperm lacking chromosome 21.
C. also has Turner syndrome.
D. is a carrier of a deletion for chromosome 21.

Answer 1

A man with trisomy 21 could pass Down syndrome to his offspring if his sperm has two copies of chromosome 21, resulting in a zygote with three copies, which is the genetic basis for Down syndrome.

Therefore, the correct statement is: A. produces sperm that have two copies of chromosome 21.

Step-by-step explanation:

A man with trisomy 21 could pass Down syndrome to offspring if he produces sperm that have two copies of chromosome 21. During gametogenesis, a person with trisomy 21 can produce gametes with an abnormal number of chromosomes due to nondisjunction.

A man with trisomy 21 could pass Down syndrome to his offspring if his sperm has two copies of chromosome 21, resulting in a zygote with three copies, which is the genetic basis for Down syndrome.

If a sperm carrying an extra chromosome 21 fertilizes a normal egg, which has one copy of chromosome 21, the resulting zygote will have three copies of chromosome 21, leading to Down syndrome.

A man with trisomy 21 could pass Down syndrome to offspring if he produces sperm that have two copies of chromosome 21.