Sickle cell disease (SCD) is found in numerous populations whose ancestral homes are in the malaria belt of Africa and Asia. SCD is an autosomal recessive disorder that results from homozygosity for a mutant β-globin gene allele. Data on one affected population indicates that approximately 8 in 100 newborn infants have SCD.
What is the frequency of carriers of SCD in the population?

Question

Sickle cell disease (SCD) is found in numerous populations whose ancestral homes are in the malaria belt of Africa and Asia. SCD is an autosomal recessive disorder that results from homozygosity for a mutant β-globin gene allele. Data on one affected population indicates that approximately 8 in 100 newborn infants have SCD.
What is the frequency of carriers of SCD in the population?

What is the frequency of carriers of SCD in the population?

Accepted Answer

Hello, everyone and welcome to today's video. So in a given population cystic fibrosis is an autosomal recessive genetic disorder which affects 250 in 1000 individuals. Let's assume that unaffected individuals do not carry the allele. So if 250 individuals get affected by the disorder, 500 are carriers where the allele frequencies of this population or the values of P and Q as answered to A, we had a P equals 0.25 Q equals 0.70 five B is P equals 0.75 Q 0.25 C. We have that P is equal to 0.50 Q equal 0.50 D. We have that P equals 0.50 Q equals 0.25. So in order to solve this problem, we need to recall the Hardy Weinberg equation which is going to be the P square, the P square plus two P Q plus Q square is going to be equal to one. So we are told that cystic fibrosis is an autosomal recessive genetic disorder which affects 250 in 1000 individuals. So this 250 in 1000 is giving us the frequency of the homozygous recessive genotype in the population, which in the Hardy Weinberg equation is going to be this Q square. So this 250 divided by 1000 is going to be equal to Q square. Now this is 0.25 is equal to Q square. If we take the square root of each side of this equation, we're going to obtain that Q is equal to 0.5. Now another form of this Hardy Weinberg equation is going to be that P plus Q is going to be equal to one. We already know that Q is 0.5. So we can input this into the equation as P plus 0.5 equals one and solve for P that P equals one minus 0.5. We know now that P is also 0.5. So the frequency of Q is 0.5 and the frequency of P is 0.5. So we were able to determine the frequencies of P and Q which if we look at our answer choices is going to be answer choice C P equals 0.5 and Q equals 0.5. I really hope this video helped you and I hope to see you on the next one.

Verified video answer for a similar problem:

Key Concepts

Autosomal Recessive Inheritance

Hardy-Weinberg Principle

Carrier Frequency Calculation