SAT Subject Biology Practice Question 129: Answer and Explanation

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Question: 129


Which individual is most likely to be a carrier of the trait in question?

A. II-2
B. II-4
C. III-2
D. III-3
E. III-4

Correct Answer: B


Individual II-4 does not exhibit the trait but has offspring who do. This means that he passed the allele for the trait to his offspring, with a likelihood of 100%, expressed as 1.0. Similar evidence is not available for the other individuals, making the likelihood that they are carriers less than 1.0.

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