You sample 40000 Tsetse flies in a forest savanna habitat in central Africa. In

Question

You sample 40000 Tsetse flies in a forest savanna habitat in central Africa. In this sample you determine that for a locus associated with Malathion resistance the flies have the genotype frequencies listed below.

M1M1: 11201       M1M2: 14800       M2M2:13999

After spraying the habitat with Malathion you obtain a sample of 5500 flies with the genotype frequencies listed below.
M1M1: 1155       M1M2: 1595       M2M2:2750


a. What are the allele frequencies in the Tsetse fly population BEFORE the Malathion spraying?

M1:

M2:

b. AFTER the Malathion spraying which allele has increased in frequency?

c. What are the relative fitnesses (W) of each genotype after the spraying?
M1M1:

M1M2:

M2M2:

Is this an example of heterozygote advantage? Why or why not.

Explanation / Answer

Allele frequency before spraying:

a)M1: {(2x11201) + 14800}/ Total Frequency = {(2x11201) + 14800}/80000 = 0.465025

M2: {(2x13999) + 14800}/80000 = 0.534975

b) after spraying

M1: 3905/11000 = 0.355

M2: 7095/11000 = 0.645

M2 allele has increased frequency

c) Fitness after spray of

M1M1: 1155/5500 = 0.21

M1M2: 1595/5500 = 0.29

M2M2: 2750/5500 = 0.5 (highest)

Relative fitness of:

M1M1: 0.21/0.5 = 0.42

M1M2: 0.29/0.5 = 0.58

M2M2 = 1

Fitness of the heterogygotes (14800/40000=0.37) does not increase after the spray (1595/5500 = 0.29). Thus, being heterozygote does not give any advantage and therefore, this not an example of heterozygote advantage.

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