Question

Based on the objective you should feel comfortable calculating expected genotype frequencies when given observed allele frequencies. You should also be able to compare expected genotype frequencies from HWE to observed frequencies and determine if evolution is occurring. Here's a sample problem. You can do this without a calculator! Let's take the noob gene, a gene with two known alleles that determines feather color in the eastern lark. The two alleles, let's call them delta and gamma, can be sequenced. In fact, looking at a population in southern GA, you discover that 60% of the alleles in the population are the delta allele. So question 1, what is the percentage of the gamma allele in the population

Answer 1

Answer:

40% is the percentage of the gamma allele in the population.

Explanation:

Available data:

• Two alleles, delta and gamma
• 60% of the alleles in the southern GA population are the delta allele

What is the percentage of the gamma allele in the population?

According to Hardy-Weinberg, the allelic frequencies in a locus are represented as p and q, referring to the allelic dominant or recessive forms. The genotypic frequencies after one generation are p² (Homozygous dominant), 2pq (Heterozygous), q² (Homozygous recessive). Populations in H-W equilibrium will get the same allelic frequencies generation after generation. The sum of these allelic frequencies equals 1, this is p + q = 1.

In the same way, the sum of genotypic frequencies equals 1, this is

p² + 2pq + q² = 1

Being

• p the dominant allelic frequency,

• q the recessive allelic frequency,

• p² the homozygous dominant genotypic frequency

• q² the homozygous recessive genotypic frequency

• 2pq the heterozygous genotypic frequency

If the percentage of delta allele in a population is 60%, this means that its frequency is 0.6. By clearing the equation p + q = 1, we can calculate the gamma allele frequency. This is:

p + q = 1

0.6 + q = 1

q = 1 - 0.6

q = 0.4

Then the percentage of gamma allele in the population is 40%.

We can also think about it like this:

If the sum of the allelic frequencies equals 1, then 1 is 100% of the allelic frequencies. And if the percentage of delta allele in a population is 60%, then 40% is the percentage of gamma allele.