1. Assuming that the average rate of neutral mutation is 10^-9 per base pair per
ID: 11474 • Letter: 1
Question
1. Assuming that the average rate of neutral mutation is 10^-9 per base pair per gamete, how many generations would it take, on average, for 20 base pair substitutions tobe fixed ina gene with 200 base pairs? Suppose that the number of base pair differences in this gene between species A and B is 92, between A and C is 49, and between B and C is 91. Assuming that no repeated replacements have occurred at any site in any lineage, draw the phylogenetic tree, estimate the number of fixations that have occurred along each branch, and estimate the number of generations since each of the two speciation events.
2. If a recessive lethal allel has a frequency of 0.050 in newly formed zygotes in one generation, and the locus is in Hardy-Weinberg equilibrium, what will be the allele frequency and the genotype frequencies at this locus at the beginning of the next generation? (Answer: q=0.048, P^2=0.9071, 2pq=0.0907, q^2=0.0023). Calculate these values for the succeeding generation. If the lethal allele arises by mutation at rate of 10^-6 per gamete, what will be its frequency at equilibrium? (Hint: The last questions is a trick question)
Please, help me.
Explanation / Answer
1. Assuming that the average rate of neutral mutation is 10^-9 per base pair per gamete, how many generations would it take, on average, for 20 base pair substitutions tobe fixed ina gene with 200 base pairs?
20/200 = 0.1
0.1(x) = 10^-9
Solve for x: x = -8
-8 implies 8 combinations aka 4 generations (on average - that's important!)
Suppose that the number of base pair differences in this gene between species A and B is 92, between A and C is 49, and between B and C is 91. Assuming that no repeated replacements have occurred at any site in any lineage, draw the phylogenetic tree, estimate the number of fixations that have occurred along each branch, and estimate the number of generations since each of the two speciation events.
2. If a recessive lethal allel has a frequency of 0.050 in newly formed zygotes in one generation, and the locus is in Hardy-Weinberg equilibrium, what will be the allele frequency and the genotype frequencies at this locus at the beginning of the next generation?
(Answer: q=0.048, P^2=0.9071, 2pq=0.0907, q^2=0.0023).
Calculate these values for the succeeding generation. If the lethal allele arises by mutation at rate of 10^-6 per gamete, what will be its frequency at equilibrium? (Hint: The last questions is a trick question)
Succeeding generation: q^2 = dominant = 0.048 x (1-0.050) = 0.0456
Therefore the "new" q = 0.0456^0.5 = 0.2135415
So now we solve for p:
0.0456 + 0.4270 p + p^2 = 1
p = 0.786491125
AT EQUILIBRIUM, frequency is ALWAYS 0% - because at equilibrium, the lethal allele is eliminated! :)
(because lethal = deadly = everyone dies off)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.