BIOL 206 Lecture Notes - Lecture 2: Allele Frequency, Genotype Frequency, Genetic Drift

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lemonweasel330

25 Aug 2016

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Chapter 6: mendelian genetics in populations i: selection and mutation. Population genetics: processes that cause changes in allele and genotype frequencies in populations. Genetic drift: variation in relative frequency of different genotypes within a small population size. P2 + 2pq + q2 = 1 p2= frequency of aa, homozygous pq= frequency of aa, heterozygous q2= frequency of aa, homozygous. Allele and genotype frequencies in an ideal population do not change from one generation to the next. This is due to the fact that the population experiences no selection, no mutation, no migration, no genetic drift, and random mating. Two fundamental conclusions can arise from it: the allele frequencies in a population will not change, generation after generation. If the allele frequencies in a population are given by p and q, the genotype frequencies will be given by p2, 2pq, q2.

Related Questions

II think this is a pretty basic Hardy-Weinberg Problem, I justdon;t know how to solve it yet. Thank you for your help!

Assume a population of 800 individuals with the followinggenotypes:452 AA, 296 Aa, and 52 aa. This is the 1stgeneration.

a. Calculate the frequencies for A___ and a___. Do this fromgenotype frequencies (do NOT assume Hardy Weinberg Equilibrium)

b. Use the allele frequencies from part a to calculate theexpected genotype frequencies for AA___ Aa___ and aa__

c. Based on your allele frequencies above, how many of eachgenotype would you expect if the population of 800 people were inHardy-Weinberg Equilibrium? AA____ Aa____aa____

d. Suppose that the original population (452 AA; 296 Aa; 52 aa)experienced an epidemic of an infectious disease that kills 75% ofeach homzygous class ( AA and aa). and 25% of the heterozygotes.How many of each genotype would survive?

e. The results of part e are still the first generation, butpost-epidemic survivors. What are the new allele frequencies?

f. Assume the 1st generation post-epidemic survivors materandomly, and there is no selection, no migration, no mutation, nogenetic drift. What frequency of each genotype is expected in the2nd generation?

g. If the 2nd generation contains 350 indivduals how many ofeach genotype do you expect?

cerisekangaroo944

Consider two populations of guppies living in a tropical stream. One is upstream of a waterfall, and the other is downstream. In both populations, homozygous individuals have either blue or red stripes, depending on the allele they carry: R for the red allele and B for the blue. RB heterozygotes have purple stripes.

In the downstream population only, there are crayfish that feed on the guppies. Because the crayfish can't see red colors, the red-striped guppies have higher fitness than blue or purple. Comparison to the upstream population, where there are no crayfish, indicates that the selection coefficient on purple and blue guppies is 0.25.

The current frequency of the R allele is 0.64. Your job is to calculate the percent change in allele frequency that occurs in the next generation due to crayfish predation. To do this you should:

a) Use the Hardy-Weinberg principle to determine expected genotype frequencies in the generation without selection

b) Determine the relative fitness of each genotype

c) Calculate the genotype frequencies in the new population following selection.

d) Find the percent change in allele frequency of the resistant R allele.

cerisesquirrel57

The current frequency of the R allele is 0.64. Your job is to calculate the percent change in allele frequency that occurs in the next generation due to crayfish predation. To do this you should:

a) Use the Hardy-Weinberg principle to determine expected genotype frequencies in the generation without selection

b) Determine the relative fitness of each genotype

c) Calculate the genotype frequencies in the new population following selection.

d) Find the percent change in allele frequency of the resistant R allele.

harlequinserval672

BIOL 206 Lecture Notes - Lecture 2: Allele Frequency, Genotype Frequency, Genetic Drift

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