Sickle-cell anemia is a genetic disorder of the blood in which the shape of red blood cells is distorted, resulting in a variety of health problems. the allele for normal blood cell production (h) is dominant to the allele for sickle cell production (h).

if one parent has sickle-cell anemia and the other parent is a carrier, what is the probability that their child will have sickle-cell anemia?

Sickle Cell Anemia is also called a recessive disorder, because if you do not have two copies of sickle hemoglobin gene, you will not have the disorder.

In this case th carrier will have one normal hemoglobin gene, and the other will be a sickle hemoglobin gene, or "Hh" in the scheme. The parent that has the disease will be labeled "hh" because he does have two copies of the sickle hemoglobin gene. When these two parents have children, none of them will be unaffected - they will either be a carrier, or will be sick. The combinations are: Hh - carrier, hh - disease, Hh - carrier and hh - disease. So, there is 50% chance that the child will have the anemia, and 50% chance that the child will be a carrier.