White flowers (genotype rr) are recessive to red (RR and Rr) in an outbreeding p
ID: 8590 • Letter: W
Question
White flowers (genotype rr) are recessive to red (RR and Rr) in an outbreeding plant species. In a large random sample, you count 200 white-flowered plants and 800 red-flowered plants. What’s the frequency of the red allele (R)? One generation later, you count 250 white and 750 red plants. What was the change in allele frequency (of r and/or R)? If this change was caused by a preference of the local pollinators (night-flying moths) for white flowers, and not by drift, or selection at some linked locus, or magic or whatever, then what were the relative fitnesses of white- flowered and red-flowered plants in the first (parental) generation?Hint: There are harder and easier ways to frame this problem. It will make your life easier if you set the fitness of red-flowered plants to 1.0, and focus on the frequency of the dominant R allele, which will then have a marginal fitness of 1.0 regardless of its frequency.
Explanation / Answer
Frequemcy before selection
RED ALLELE-R, WHITE -------r
Red is dominat over recessive white
RR, Rr, rr
red-flowered plants-----------800----------- RR, Rr
white-flowered plants------200-------------- rr
Frequemcies of alleles ---
-according HARDY WEINBERG--------- p2+2pq+q2
white-flowered plants------200-------------- rr---------- q2
Frequemcies of recessive allele(white ,r )= square root of 200/1000= .2= 0.44
P+q=1
P=1-44=.56
Red allele frequency ---------0.56
One generation later, you count 250 white and 750 red plants. What was the change in allele frequency (of r and/or R)
After one generation
red-flowered plants-----------750----------- RR, Rr
white-flowered plants------250-------------- rr
Frequemcies of alleles ---
-according HARDY WEINBERG--------- p2+2pq+q2
white-flowered plants------250-------------- rr---------- q2
Frequemcies of recessive allele(white ,r )= square root of 250/1000= .25= 0.5
P+q=1
P=1-.5=.5
Red allele frequency ---------0.5
BEFORE AFTER
R 0.56 0.5
r 0.44 0.5
Fitnees = number of alleles( after)/ number of alleles( before)
R –Fitnees= 0.5/0.56=0.89, r –Fitnees= 0.5/0.44=1.13
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