Question

1.

In the White Sands desert of New Mexico, light coloration has evolved in multiple, independent populations of mice, similar to the lizards described by Rosenblum et al. (2010). In some cases, a mutation in the Mc1R gene prevents binding of a signaling molecule, thus blocking the signal to produce melanin. This type of mutation appears to be recessive. In other cases, increased production of the inhibitor ASP blocks production of melanin. This type of mutation appears to be dominant. In a third type of population, a mutation affecting the melanin pathway creates light coloration in heterozygotes and homozygotes, but also has very detrimental effects on the immune system in individuals that are homozygous. In the table below, A1 represents the normal allele and A2 represents the mutation for each case.

a.Fill out the table below with fitness values for each genotype. You may use only these three numbers to represent fitness values: 1, 0.8, 0.6. For each column in the table, choose fitness values that are consistent with the given scenario. (Note: There may be more than one correct way to do this).

b.For the Mc1R mutation, state the value of the selection coefficient s that is consistent with the numbers you have chosen to represent fitness :________

c.For the melanin pathway/immune system mutation, solve for the equilibrium value of p (the frequency of allele A1) given the numbers you have chosen to put in your table. Show your work:

Table1:

Genotype	Mc1R mutation	ASP Mutation	Melanin pathway/immune system mutation
A1A1
A1A2
A2A2

Answer 1

a.

GENOTYPE	Mc1R mutation	ASP mutation	Melanin pathway
A1A1	0.6	1	0.6
A1A2	0.8	0.8	1
A2A2	1	0.6	0.8

b.

GENOTYPE	A1A1	A1A2	A2A2
SELECTION COEFFICIENT	0.4	0.2	1

( 1 - 0.6 ) ( 1 - 0.8 )    ( 1 )

c.

frequency of p ( A1) = 0.6/2.4

= 0.25