CAS BI 107 Lecture Notes - Lecture 3: Allele, Gene Pool

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cerisegiraffe538

18 Sep 2015

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Allele and genotype frequencies changing = evolution. Gene/allele frequency: distribution of a and a. Measure the amount of genetic variation in a population. Genotype frequency: distribution of individuals who are aa, aa, aa. Shows how a population"s genetic variation is distributed among its members. Pea plants: crossover between purple flowers and white flowers. P = (number of copies of the allele in the population) / (sum of alleles in the population) If a locus has two alleles, a and a, there could be three genotypes: aa, aa, and aa. P is the frequency of allele a, and q is the frequency of allele a. If p + q = 1, then (p + q)2 = 1 and p2 + 2pq + q2 = 1. If the calculated p^2, 2pq, and q^2 values are not the same as the observed frequencies, the population did not remain in hw equilibrium. P (frequency of a allele): [2(40) + 20] / 200 = 0. 5.

Related Questions

State how genetic drift, admixture, and natural selection are expected to influence the distribution of genotype and allele frequencies within and among populations?

pucehamster827

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

1 Explain at least 3 ways that selection can preserve genetic variation.

2 Explain how selection affects differently: dominant vs recessive traits; homozygotes vs heterozygotes; and when frequency-dependence is a factor.

3 What is the source of genetic variation? How does meiosis contribute to maintenance of genetic diversity?

4Describe the preconditions for natural selection to operate and what the results of natural selection will be.

5 Use the HW equations to solve simple population genetics problems with and without selection.

6 Hardy-Weinberg equilibrium tells us the conditions under which populations will not evolve. So what types of things may lead to a population evolving? How do these things lead to populations evolving (gene frequencies changing)?

7 When is genetic drift the strongest?

CAS BI 107 Lecture Notes - Lecture 3: Allele, Gene Pool

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