Question

C) This mutation is a recessive trait. What is the likelihood that a woman who does not possess the sickle cell trait and a man who is a carrier of the sickle cell trait will have a child who suffers from sickle cell anemia? Explain your answer.

Answer 1

What is Sickle cell anemia?

Sickle cell is an autosomal recessive trait of humans that arises through mutation in normal gene. The gene for this trait is found in recessive form and you need two copies of the gene - one from father and one from mother- to have the trait expressed. If the trait is expressed it causes a disease called sickle cell anemia.

People with the sickle cell anemia disease have red blood cells of crescent or sickle shape. The red blood cells of this shape can cause many complications in body. They get stuck in blood vessels and cause pain. They also die quickly and make a person anemic (pale).

Probability to have a child with sickle cell anemia:

If a mother is normal but a father is carrier for the trait,  then the situation will be as:

Here N indicate normal allele, S indicate allele for sickle cell anemia.

                                    Mother           ˣ                            Father

                                      NN                                                 NS

Gametes:            N             N                                  N                S

Offspring:           NN             NS                             NN                     NS

                                                50% :                  Normal

                                                50% :                  Carrier

                                                0%    :                 Sickle cell anemia

It means that 50 % kids will be normal and 50% will be carrier for the trait and none of the offspring will have disease Sickle cell anemia. However, those who are carriers can carry the disease to the next offspring if they are married to a carrier or a person with sickle cell anemia.