4. In a population of gumbo gnats, 2 alleles are segregating at an X-linked locu

Question

4. In a population of gumbo gnats, 2 alleles are segregating at an X-linked locus that determines eye color. A is the allele for yellow eyes and is partially dominant to a, the allele for blue eyes. In gumbo gnats, females are the homogametic sex. The following population sample was collected:

Gen. 0

Eye Phenotypes # Females #males

AA (yellow) 20 0

Aa 0 0

aa 0 20   

A) What is the frequency of the A allele in this population.

B) What is the frequency of A in females, pf = ?

C) What is the frequency of A in males, pm = ?

D) If random mating occurred, what would the allele frequencies in each sex be in

the next generation (Gen. 1)? What would the genotype frequencies be?

E) If random mating occurred in Gen. 1, what would the genotype and allele

frequencies be for each sex in Gen. 2? How does pm in Gen. 2 compare to pf in

Gen. 1?

F) Graph pf and pm over Gen. 0, 1, and 2. Can you predict what pf and pm will be at

Gen. 10?

Explanation / Answer

Based on the given data,

The two alleles are X-linked and “A” is the allele for yellow eyes is dominant over “a”, the allele for blue eyes.

The females are homogametic sex: “AA” (yellow) and “aa” (blue eyes)

The males are heterogametic sex: “Aa” (yellow eyes)

The

Thus, the total population size is: 40.

Genotype frequencies are calculated as:  

The allele frequencies are calculated as:

A) Thus, the allele frequency of “A” in in this population = 0.5

B) Thus, the allele frequency of “A” in females, pf is = 0.5

C) Thus, the allele frequency of “A” in males, pm is = 0

D)

The allele frequencies in each sex are in the first generation:

The genotype frequencies are:

E)

The allele frequencies in each sex are in the second generation:

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