Question

In a population of 200 flies you gathered the following information:

45 Homozygous Purple, 50 Heterozygous Purple, 105 Homozygous green. Using this information fill in the chart below and answer the questions


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Answer 1

Here is the information filled into the chart:

Genotype Number of Flies Percentage

pp 45 22.5%

Pp 50 25%

PP 105 52.5%

Total 200 100%

What is the frequency of the dominant allele P in the population?

The frequency of allele P is computed as 2 times the percentage of heterozygous flies (Pp) plus the percentage of homozygous dominant flies (PP).

So the frequency of P is:

2(25%) + 52.5% = 103%

What is the frequency of the recessive allele p in the population?

The frequency of allele p is computed as the percentage of homozygous recessive flies (pp).

So the frequency of p is:

22.5%

What is the probability that two flies chosen at random would produce heterozygous offspring?

Since 25% of the flies are heterozygous (Pp), the probability of choosing a Pp fly is 0.25.

The probability of choosing two Pp flies is (0.25)x(0.25) = 0.0625

But heterozygous offspring can also be produced by choosing a PP fly and a pp fly.

The probability of choosing a PP fly is 0.525 and a pp fly is 0.225.

So the probability of choosing those two flies is (0.525)(0.225) = 0.118

Adding the two probabilities:

0.0625 + 0.118 = 0.1805

So the probability that two flies chosen at random would produce heterozygous offspring is 0.1805 or 18.05%.