Question

Sickle-cell anemia is an autosomal recessive disease. A man whose father had sickle-cell anemia but who does not himself have the disease marries a woman whose mother had sickle-cell anemia but who does not herself have the disease. Which of the following statements is FALSE?

About three-fourths of their offspring, on average, can be expected to have at least one sickle-cell allele.
They can produce offspring that are neither carriers of the trait nor affected with sickle-cell anemia.
If their first two children do not have sickle-cell anemia, the chances of the third having the disease are 1 in 4.
All of their offspring must be carriers of the sickle-cell allele.

Answer 1

The statement that is FALSE is: All of their offspring must be carriers of the sickle-cell allele.The statement that is FALSE is: All of their offspring must be carriers of the sickle-cell allele.

Step-by-step explanation:

The statement that is FALSE is: All of their offspring must be carriers of the sickle-cell allele.

Sickle-cell anemia is an autosomal recessive disease, which means that both parents must be carriers in order for their offspring to have the disease. However, since the man does not have sickle-cell anemia and the woman does not have sickle-cell anemia, it is possible for their offspring to be neither carriers nor affected with sickle-cell anemia. So, the statement that three-fourths of their offspring can be expected to have at least one sickle-cell allele is true, as is the statement that they can produce offspring that are neither carriers nor affected with sickle-cell anemia. Also, if their first two children do not have sickle-cell anemia, the chances of the third having the disease are 1 in 4, which makes the statement true as well.