Question

What conditions must exist for a person to have sickle cell disease?

Responses
A A person with sickle cell disease has inherited at least one copy of the mutated gene.A person with sickle cell disease has inherited at least one copy of the mutated gene.
B The chromosomes responsible for sickle cell disease must be subjected to a mutagen.The chromosomes responsible for sickle cell disease must be subjected to a mutagen.
C A person with sickle cell disease has inherited two copies of the gene having the mutation.A person with sickle cell disease has inherited two copies of the gene having the mutation.
D A person with sickle cell disease has inherited two copies of the gene having the mutation that may or may not influence the hemoglobin protein.

Answer 1

C.

Sickle cell disease is autosomal recessive — affected people have two mutated HBB alleles (for example HbSS). Carriers (one mutated copy, HbAS) usually have the sickle cell trait but not the full disease. (Compound heterozygotes such as HbS/HbC or HbS/β-thalassemia also cause disease because two abnormal β‑globin alleles are present.)