6. Imagine that in a population of morning glory flowers, a recessive mutation o
ID: 52001 • Letter: 6
Question
6. Imagine that in a population of morning glory flowers, a recessive mutation occurs that changes flower color from purple to white at a frequency of 10–4.
a) If there is no selection on coloration, what would be the frequency of the purple allele after one generation, if it starts at a frequency of 0.90?
b) If there is selection against the white flowers, and it is recessive, what frequency will the white flower allele eventually reach? Imagine that the selection coefficient is 0.4 acting against this white coloration allele.
c) In another population there is also selection against the homozygous purple flower genotype individuals. If the selection coefficient acting against this purple homozygote is 0.2 while the selection against the white homozygote is still 0.4, then what is the stable equilibrium frequency of the white allele in this population (ignoring mutation for this question)?
Explanation / Answer
(a) The frequency of the purple allele will remain the same in the next generation.The Hardy-Weinberg principle predicts that allelic frequencies remain constant from one generation to the next, or remain in EQUILIBRIUM, if we assume certain conditions.Therefore in the next generation it wiil remain 0.90.
(b)
As per HARDY-WEINBERG EQUILIBRIUM
p + q = 1
given value of p = 0.9
therefore q = 0.1
selective coefficient s is mentioned as 0.4
frequency of the white flower allele on selection is represented by q1 and calulated by the give formula
q1 = [2(1-s)q2 + 2pq]/ 2(1-sq2)
p = 0.9
q = 0.1
s = 0.4
q1 = 16
hence on selection frequency of the white flower allele will reach 16
C. If there is selection against the 'a' allele, the allele frequencies will reach stable equilibrium only once 'a' is completely removed from the population. Only mutation will return a to the pool, resulting in further selection.
As there is no mutation, the stable equilibrium frequency of the white allele in this population is 0.
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