# Population Genetics

3. In plants, flower color is controlled by incomplete dominance, where red and blue are the two homozygous conditions and purple indicates heterozygous. An initial population contains 14 red, 70 purple, and 24 blue individuals. Give exact allele and expected genotype frequencies for this population. Now assume that the heterozygous condition confers frost resistance to these plants. After a cold snap, 50% of the homozygous (as in 50% of the red and 50% of the blue) and 10% of the heterozygous plants die. Determine the new exact allele and expected genotype frequencies.

4. In a population of chickens, 23% carry a recessive allele for red legs but only 7% express the trait. Determine p and q, and the expected genotype frequencies.

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#### Solution Preview

3. Let us use R for red and B for blue.

We can write out the population as this:

RR= 14

RB = 70

BB = 24

What do we have?

We have 14 + 14 + 70 = 98 R alleles.

We have 70 + 24 + 24 = 118 B alleles.

There is a total of 216 alleles.

Therefore, the exact allele frequencies are (98/216) = 0.45 for R allele, and (118/216) = 0.55 for B allele.

According to Hardy-Weinberg, p^2 + 2pq + q^2 = 1, where p^2 is RR, 2pq is RB, and q^2 is BB.

Therefore, the genotype frequencies are:

RR = 0.45^2 = 0.20

RB = 2(0.45)(0.55) = 0.50

BB = 0.55^2 = 0.30

Now, after the cold snap, we have an adjusted population: 50% of the homozygous (as in 50% of the ...

#### Solution Summary

The expected genotype frequencies in population genetics are examined.