BSC 315 Lecture Notes - Lecture 29: Natural Selection, Balancing Selection, Allele Frequency

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graysardine594

25 Apr 2016

School

University of Alabama

Department

Biological Sciences

Course

BSC 315

Professor

Edwin Stephenson

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Document Summary

Population genetics- allele frequencies in populations and mechanisms of change over time. Evolution- change in allele frequency w/in a population over time. A static view of allele frequency: the hardy-weinberg equation. What are the frequencies of genotypes a/a and a/a. If a/a = q2 = . 36, then q = 0. 6. Since p + q = 1, p = 0. 4. A/a = 2pq = 2 x (0. 4) x (0. 6) = 0. 48. If one genotypic frequency is known, all others can be calculating (assuming the population is in equilibrium) The population is stable and allele frequencies don"t change over time. If so, allele frequencies can be calculated using the h-w equation. Since all are never true, h-w is an approximation. Basic h-w formula is modified to account for these. Change in allele frequency over time = evolution. Evolution occurs when the assumptions in hardy weinberg equilibrium are violated:

Related Questions

Consider a wildflower population with the following allele and genotype frequencies.

Frequency of the C^Rallele: p = 0.6

Frequency of the C^Wallele: q = 0.4

Frequency of C^RC^R: 50%

Frequency of C^RC^W: 20%

Frequency of C^WC^W: 30%

Is this population in Hardy-Weinberg equilibrium?

No, the frequency of genotype C^RC^Wis too low.

No, the frequency of genotype C^RC^Ris too low.

Yes, the genotype frequencies are what we would expect for a population in Hardy-Weinberg equilibrium.

No, the frequency of genotype C^WC^Wis too low.

magentaweasel586

Q1. What are alleles?Different forms of the same gene.Different genes.The different characteristics of an organism.Genes found only in humans.Q2. If you add up the frequency of homozygotes + the frequency of heterozygotes for one gene (i.e. at one locus) in a population, what number do you get?Q3. People who are heterozygous for the sickle-cell allele:Are susceptible to malaria but not sickle-cell anemia.Are susceptible to sickle-cell anemia but not malaria.Are not susceptible to either sickle-cell anemia or malaria.Are susceptible to both sickle-cecell anemia and malaria.Q4. In the case study in this lab, which genotype is represented by "2pq" in the Hardy-Weinberg equation?Homozygous HbAHomozygous HbSHeterozygous HbA/HbSNo specific genotypeQ5. Suppose that, in an isolated village, the proportion of individuals that have sickle-cell anemia is 0.1 (or 1 of every 10 people). What proportion of the population should be sickle-cell carriers, according to Hardy-Weinberg expectations?Q6. When you simulated the elimination of malaria at the beginning of the lab, once the allele frequencies stabilized, what was the frequency of the HbA allele?Q7. When you investigated regional differences, what was the frequency (over many generations) of the HbS allele in the village in the "slightly wet" part of Africa?Q8. What is the number of deaths due to sickle-cell anemia in a region without mosquitoes expected to be?Very lowVery highModerateRelated to the frequency of malaria allelesQ9. As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time?Because natural selection changes all allele frequencies in populations over time.Because genetic drift causes random fluctuations of allele frequencies in populations.Because diseases will eliminate some of the alleles, generating fluctuations in their frequencies.Because allele frequencies fluctuate before the alleles eventually become fixed.Q10. Imagine a huge population with a gene that has ten functionally equivalent, neutral alleles. A small but genetically representative group of individuals from the big population is transported to an island, forming a small population. Which of the statements below best describes what will likely happen over time, and why?Because natural selection doesn't act on neutral alleles, the frequencies in the two populations should remain the same over time.Genetic drift will cause one allele to first become fixed in the island population, and later to become fixed in the original, large population.Genetic drift will result in the allele frequencies of the two populations diverging over time, with alleles being lost sooner in the island population.The allele frequencies of the two populations will change similarly due to a combination of genetic drift natural selection.

indigosnake469

A population of butterflies has an allele B for big spots on the wings and b for small spots on the wings. The table below provides data about this population.

Genotype	BB	Bb	bb
Number of butterflies	300	400	300
Genotype frequency	0.3	0.4	0.3

Regarding these data about the butterfly population, which of the following statements is correct?

1-The population is not in Hardy-Weinberg equilibrium because the genotype frequency of bb is greater than it would be in equilibrium.

2-The population is in Hardy-Weinberg equilibrium because the number of B alleles is equal to the number of b alleles.

3-The population is not in Hardy-Weinberg equilibrium because p ² and 2pq are different.

4-The population is in Hardy-Weinberg equilibrium because half of the heterozygotes are B and half are b.

BSC 315 Lecture Notes - Lecture 29: Natural Selection, Balancing Selection, Allele Frequency

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