If two carrier parents have a child for a recessive disorder, what is the theoretical chance of an affected child?
Answer and explanation
Correct answer: One fourth
Let the normal dominant allele be A and the recessive disease allele be a. Two unaffected carriers have the genotype Aa, so the cross is Aa × Aa. The possible offspring genotypes are AA, Aa, Aa, and aa. Only aa expresses a recessive disorder, giving 1 affected outcome out of 4, or 25%. Therefore, option A is correct.
Frequently asked questions
What is the correct answer to this question?
One fourth
Why is this the correct answer?
Let the normal dominant allele be A and the recessive disease allele be a. Two unaffected carriers have the genotype Aa, so the cross is Aa × Aa. The possible offspring genotypes are AA, Aa, Aa, and aa. Only aa expresses a recessive disorder, giving 1 affected outcome out of 4, or 25%. Therefore, option A is correct.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: World of Living. Topic: Heredity and Evolution.
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