Multiple Choice
Why are pedigrees useful in understanding how organisms inherit traits?
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13. Mendelian Genetics
Pedigrees
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In a pedigree for a rare autosomal recessive trait, what is the probability that individual A is a carrier?
A
25%
B
75%
C
100%
D
50%
Verified step by step guidance1
Understand that an autosomal recessive trait requires two copies of the recessive allele for the trait to be expressed. A carrier has one copy of the recessive allele and one copy of the dominant allele.
Identify the parents of individual A in the pedigree. If both parents are carriers, they each have one dominant and one recessive allele.
Use a Punnett square to determine the possible genotypes of individual A. The parents can pass on either the dominant or recessive allele.
Calculate the probability of individual A being a carrier. In a Punnett square, there are four possible combinations: two combinations result in carriers, one results in a homozygous dominant individual, and one results in a homozygous recessive individual.
Determine the probability of individual A being a carrier by dividing the number of carrier combinations by the total number of combinations. This gives a probability of 50%.
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