Question

Sickle cell anemia is inherited as an autosomal, recessive disorder. Individuals who inherit the mutated gene from both parents will show symptoms of sickle cell, including a stiffening of the red blood cells when the individual is under conditions with low oxygen levels in the air (e.g. on top of a mountain). This can lead to low red blood cell count (anemia), shortness of breath, fatigue, jaundice, and joint pain. Most critically, the stiffened red blood cells can clog small blood vessels, blocking blood flow to critical organs (e.g. brain, lungs, liver, etc.) that can lead to death. Curiously, heterozygous carriers have a certain amount of resistance to malaria. The malaria parasite must invade red blood cells in order to develop and apparently the cell surface is altered in heterozygous individuals, thereby limiting the ability of the malaria parasite to enter the red blood cells. Recall that the rules for autosomal recessive diseases are that only the homozygous recessive individuals experience the symptoms of sickle cell anemia.

. Determine the results of a mating between a person with sickle cell anemia and an individual who is heterozygous.

Provide the Punnett square and the potential offspring phenotypes and genotypes.

What percentage of children from this mating will develop sickle cell anemia?

What percentage of children from this mating will carry at least one sickle cell allele?

Answer 1

Let us assume the recessive allele is "a" and the dominant allele is represented by "A". Since in the question it is given that one of the parent is having sickle cell disease therefore the genotype will be "aa" and the other parent is heterozygous therefore the genotype will be " Aa".

The punnett square will possible genotypes of offsprings is shown below in the picture:

• Out of these offsprings, the ones with genotype Aa(heterozygous)will be carriers.
• And the offsprings with genotype aa will suffer from sickle cell disease.

=> Percentage of children who will develop sickle cell anemia is - 50%

=> Percentage of children who will carry at atleast one sickle cell allele- 50%