The frequency of tasters and nontasters of PTC varies among populations. In population A, 64% of people are tasters (an autosomal dominant trait) and 36% are nontasters. In population B, tasters are 75% and nontasters 25%. In population C, tasters are 91% and nontasters are 9%.
Calculate the frequency of the dominant (T) allele for PTC tasting and the recessive (t) allele for nontasting in each population.

Question

The frequency of tasters and nontasters of PTC varies among populations. In population A, 64% of people are tasters (an autosomal dominant trait) and 36% are nontasters. In population B, tasters are 75% and nontasters 25%. In population C, tasters are 91% and nontasters are 9%.
Calculate the frequency of the dominant (T) allele for PTC tasting and the recessive (t) allele for nontasting in each population.

Calculate the frequency of the dominant (T) allele for PTC tasting and the recessive (t) allele for nontasting in each population.

Accepted Answer

Hello everyone and welcome to today's video. So in a population of butterflies, the spotted wing phenotype is determined by a recessive allele, lower case s while the solid wing phenotype is determined by a dominant allele, which is upper case S so a 35% of the butterflies have this spotted wing phenotype. What are the allylic frequencies of the upper case and lower case S ali in the population? So as answer choice A we have that the dominant allele is 0.59. The recessive is 0.41. As answer choice B we have that the dominant is 0.35 recessive 0.65. As answer choice C we have that the dominant is 0.65 the recessive 0.35. And as answer choice D we have that the dominant is 0. while the recessive is going to be 0.59. Now, in order to solve this problem, we need to recall the Hardy Weinberg equation which is going to be P square plus two P Q plus Q square is going to be one. Now, in the problem, we are told that the spotted wing phenotype is going to be recessive. So it's going to be a recessive genotype. Now, the recessive genotype in the Hardy Weinberg equation is given by Q square, so Q square is going to be 35% which is what the frequency of this genotype is given to be in the population. So Q square is 0.35. If we find the square root of both sides, we can determine that Q is going to be equal to 0.59. So now we determine Q which recall from previous videos is going to be the frequency of the recessive ali or the lower case S in the population. Now let's move on to find the frequency of the dominant AO we have that P plus Q is going to be one. If we input this into this equation, we can see that P is going to be equal to one minus Q P is going to be equal to one minus 0. P is going to be equal to 0.41. So we were able to determine that the dominant AO is 0.59 while the, or that the recessive AO is 0.59 while the dominant AO is 0.41. And if we look at our answer choices, this is going to be represented by answer choice. T dominant Ali 0.41. Recessive A 0.59. I really hope this helped and I hope to see you on the next video.

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Key Concepts

Hardy-Weinberg Principle

Allele Frequency Calculation

Phenotypic Ratio