Question

Please answer ALL questions:

If a man with sickle cell anemia has a child with a woman who is a carrier, what is the probability that their child will be a carrier?

A

25%

B

50%

C

75%

D

100%

If a man with sickle cell anemia has a child with a woman who is homozygous for the normal Hballele, what is the probability that their child will be sickle-cell anemic?

A

0%

B

25%

C

50%

D

100%

If a man with sickle cell anemia has a child with a woman who is homozygous for the normal Hballele, what is the probability that their child will be a carrier?

A

0%

B

25%

C

50%

D

100%

Your father has just been diagnosed with Huntington disease, an extremely rare dominant disorder. What are the chances that you will develop this disease when you hit midlife? (Hint: choose the parental genotypes based on the fact that the disease allele is extremely rare!).

A

0%

B

25%

C

50%

D

100%

Answer 1

Question 1 :-

Sickle cell anemia is a recessive disease. So the man is homozygous for the HbS allele (Sickle cell hemoglobin) and woman is a carrier which mean she's Heterozygous with one allele for HbS and other for normal Hb allele.

In a cross of this, 2 out of 4 children will be carriers. So the answer is 50%.

Question 2:-

In this question, woman have normal HbA alleles and is homozygous for it. In a recessive disorder to be inherited, both the parents need to have atleast 1 allele for the disease.

So in this case, all the offspring will be Carriers but no one will have the disease.

So the right answer is 0%

Question 3:-

Like in Question 2, I said that all the children will be Carriers.

So the right answer is 100%

Question 4 :-

It's a dominant trait, so one Allele is enough for disease to manifest and considering that it's a rare allele, Father have only 1 copy of the diseased allele and mother probably is a normal healthy individual.

So, if we do a punett square of it, there are chances that 2 out of 4 children will have it.

So the right answer is 50%