Mutation Rate Genetics problem plz help :)

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xbgbabex13
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Mutation Rate Genetics problem plz help :)

Post by xbgbabex13 » Fri Feb 11, 2011 3:48 am

Consider a population with the frequency of the A allele at 0.7 and the a allele at 0.3.
a.Assume that this population is undergoing mutational pressure. The rate of mutation is 1.0 x 10-4 for changing A to a and 1.0 x 10-5 for changing a to A. What is the allele frequency of A after a single generation? (do not round your answer)
b.What will the allele frequencies be in the next generation if the forward mutation rate (A to a) and the back mutation rate (a to A) are equal?

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DRT23
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Post by DRT23 » Sat Feb 26, 2011 7:31 pm

I hope it is not late for an answer. Since I'm an undergraduate student and have never come across this kind of a question, my answer may be false. But, I used basic reasoning, some mathematics and of course a calculator :) So, it's highly probably correct.

Frequency of allele A: 0.7
Frequency of allele a: 0.3
Total: 1 (which is a rule)

Mutation from A to a: 0.7 x 1.0 x 10-4 = 0.000070
Mutation from a to A: 0.3 x 1.0 x 10-5 = 0.000003
Justified shift : ................... = 0.000067 (0.000070 - 0.000003) from A to a.

Which means more A's became a. Thus, frequency of A must decrease and frequency of a must increase:

Final frequency of allele...
A = 0.7 - 0.000067 = 0.699933
a = 0.3 + 0.000067 = 0.300067
Total = ............. = 1.0 (which is a rule as I said above)

So, you can answer your second question now. Since the justified shift (this is not a scientific term, I coined it :) ) will be 0, allele frequencies don't change in this circumstance.

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