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).

Question

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?

Hint: Use the Punnett square below to help you.
H h
h ? ?
h ? ?
A.
75%
B.
50%
C.
25%
D.
100%

Answer 1

To determine the probability that the child will have sickle-cell anemia, we can use a Punnett square to analyze the genetic makeup of the parents.

Given:

• One parent has sickle-cell anemia: genotype (hh)
• The other parent is a carrier (heterozygous): genotype (Hh)

We'll set up the Punnett square:

      H    h
    ___________
h |   Hh   |  hh  |
    ___________
h |   Hh   |  hh  |

From the Punnett square:

1. The combinations from the squares are:

   • Hh (carrier, does not have sickle-cell anemia)
   • hh (has sickle-cell anemia)

2. Counting the outcomes:

   • 2 out of 4 squares yield Hh (carrier)
   • 2 out of 4 squares yield hh (has sickle-cell anemia)

This means there is a probability of 2 out of 4 (or 50%) that the child will have sickle-cell anemia.

So, the answer is:

B. 50%