Large leopard frogs ( Lithobates pipiens ) outcompete smaller frogs for mates, b

Question

Large leopard frogs (Lithobates pipiens) outcompete smaller frogs for mates, but small leopard frogs are able to sneak some matings, undetected by the large males. Mid-sized males are too small to overpower the large males but too large to sneak matings. Accordingly, large males (AA) were assigned a relative fitness of 1; small males (aa), a relative fitness of 1-s1; and mid-sized males (Aa) a relative fitness of 1-s2. The selection co-efficients s1 and s2 = 0.1 and 0.2, respectively. Assuming that initially p = 0.5, and q = 0.5, and all the conditions of the Hardy-Weinberg principle are met, what would be the relative contributions of each genotype to the next generation? Show your work.

B) how many of each genotype would be expected in this next generation in a population of 1867 frogs?

AA:_____________ Aa:_____________   aa: _____________

Bonus (2 marks): what kind of dominance is this?

Explanation / Answer

If the population is in Hardy Weinberg equiibrium, then expected henotype frequencies can be calculated from the given value pf p and q

OBSERVED GENOTYPE FREQUENCIES :

AA = p2 = (0.5)2 = 0.25

Aa = 2pq = 2(0.5)(0.5) = 0.5

aa = q2 = (0.5)2 = 0.25

Now, Allele frequencies will be calculated:

ALLELE FREQUENCY

Frequency of A = p= p2 + 1/2 (2pq) = 0.25 + 1/2 (0.5) = 0.25

Frequency of a =q = q2 + 1/2 (2pq) = 0.25 + 1/2 (0.5) = 0.25

EXPECTED GENOTYPE FREQUENCY

AA = p2 = (0.5)2 = 0.25

Aa = 2pq = 2(0.5)(0.5) = 0.5

aa = q2 = (0.5)2 = 0.25

EXPECTED NUMBER OF INDIVIDUAL OF EACH GENOTYPE

AA = 0.25 * 1867 =466.75 = 467

Aa = 0.5 *1867 = 933.5 = 934

aa = 0.25 * 1867 =466.75 = 467

These will be the expected number of Frogs of each genotype if the population is in Hardy Weinberg equilibrium.

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