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Biological Sciences

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Evolution

Question
4 out of 6
 

The ability to taste phenylthiocarbamide (PTC) is determined by the T gene. Homozygous dominant individuals (TT) experience PTC as a very strong and unpleasant taste. Heterozygotes (Tt) can taste PTC but experience it as a much weaker taste do not find it quite as offensive. Homozygous recessive individuals (tt) cannot taste PTC at all. As a class assignment, students were tested for their ability to taste PTC, and were asked to test their parents as well. The class data was pooled and the results are shown in the following table:

Ability to taste PTC

Students

Parents

Strong taste

6

11

Weak taste

4

14

No taste

10

15

The class then examined the data and calculated allelic and genotypic frequencies, based on the formulas related to Hardy-Weinberg equilibrium.


Is this population in Hardy-Weinberg equilibrium for the ability to taste PTC?

A Yes, as the allelic frequencies are relatively the same in each generation.
B No, as strong tasters do not occur with the same frequency in each generation.
C No, as the values of p and q in the student generation are not equal.
D No, as the values of p and q are not the same in each generation.
Ans. D

Remember that a population is said to be in Hardy-Weinberg equilibrium if allelic frequencies do not change. Here we see that the values of p and q are different from one generation to the next. It does not require that the genotypic frequencies be the same in each generation (response B).

Evolution Flashcard List

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