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? a. 100% b. 50% c. 75% d. 25% punnet square h h h ? ? h ? ?

B) 50% chance of the child having the disease. 
This is because the parent who is a carrier must have Hh. The parent who has the disease must be hh (as it's a recessive disease, so you can only have it if you have no H).
If you draw this punnet square and fill in the blanks:
   x        H          h
   h

   h

You will get:
1) Top left = Hh (child does NOT have the disease)
2) Bottom left = Hh (child does NOT have the disease)
3) Top right = hh (HAS disease)
4) Bottom right = hh (HAS disease)
Therefore 1 in 2 chance (50%)