The ability to taste PTC comes from a single dominant allele. A population of 20

Question

The ability to taste PTC comes from a single dominant allele. A population of 20 individuals was surveyed to find out if individuals were tasters or non-tasters. Of those surveyed, 16 out of 20 were able to taste PTC. Let T refer to the allele that confers tasting ability and t refer to the non-taster allele. Assuming that Hardy-Weinberg conditions are met, please answer the following questions. Give all of your answers as frequencies and round all of your answers to 2 decimal digits. (Rounding rules: When rounding to 2 digits, look at the third decimal digit. If the third digit is 5 or greater, round up. If the third digit is 4 or less, round down.)
What is the frequency of the non-taster allele (t) in this population?  

What is the frequency of the taster allele (T) in this population?  

What is the frequency of the TT genotype?  

What is the frequency of the Tt genotype?  

What is the frequency of the tt genotype?  

How many people in this population are expected to be heterozygous for this locus?

Explanation / Answer

Given that, the total number of population is = 20

Of which four are nontaster, means they are homozygous recessive, q2 = 4

The proportion of recessive individuals in the population q2 = 4/20 = 0.2 or q = 0.447 or approximately 0.45

As p+q = 1, p = 1-0.45 = 0.55

p = Frequency of dominant allele = 0.55

The frequency of the faster allele (T) = 0.55

The frequency of TT genotype = 0.55*0.55 = 0.3

Frequency of Tt genotype (2pq) = 2* 0.55* 0.45 = 0.494 or approximately 0.5

Frequency of tt genotype = 0.45* 0.45 = 0.2

50% of people (since 2pq = 0.5) heterozygous for this locus.

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