CAS BI 107 Lecture Notes - Lecture 3: Genotype Frequency, Allele Frequency, Heterozygote Advantage

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yellowbadger355

25 Aug 2016

School

Boston University

Department

Biology

Course

CAS BI 107

Professor

Wasserman, Mullen, Spilios, Sorenson

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Document Summary

These are how biologists measure evolutionary change! Genotype frequencies show how genetic variation is distributed among members of a population. Important distinction: allele frequency (also gene frequency): % a vs % a, genotype frequency: % aa vs % aa vs % aa. Hardy-weinberg equilibrium is a model where allele frequency does not change, enabling biologists to calculate genotype frequencies from allele frequencies. Hardy-weinberg equilibrium requires : no mutation, no selection among genotypes, no gene flow, infinite population size, random mating (no sexual selection) Fitness is the contribution of a genotype to the next generation: combines reproductive success and survival rate into one data point. Violates hardy-weinberg equilibrium involves non-random mating. Reduces the number of heterozygotes by half each generation. After a generation of inbreeding : evolution has not occurred! Allele frequencies remain the same: the population is not in hardy-weinberg equilibrium the genotype frequencies are not consistent with hwe predictions.

Related Questions

In 1908 Hardy and Weinberg published papers showing that the binomial or multinomial could be applied in genetics to predict the frequencies of genotypes when allele frequencies where known. The formal algebraic proof of this Hardy-Weinberg Equilibrium Law assumes that there is no mutation in the population. This assumption is necessary, because a. organisms reproduce sexually and litter or family sizes vary. b. populations will exhibit random sampling changes in allele frequency. c. populations are not infinite and the Hardy-Weinberg proof is only a very crude approximation when natural selection is acting. d. populations are not closed and reproduce both sexually and asexually so an infinite size population is required to preserve genetic variation. e. allowing alleles to change would alter their frequencies.

amethystcrab894

6. Red-footed boobies vary in plumage color. For simplicity, letâs pretend that there are two forms. Brown birds have darker plumage because they are genotypically either MM or Mm. White birds have light plumage because they carry the genotype mm.

You go out to Genovesa Island with a pair of binoculars and you count the number of melanic and white boobies out of the first 1000 birds you see. You count 490 white boobies and 510 melanic boobies.

a. Assuming HWE, what is the frequency of the M allele of the plumage color gene?

Next, you collect feathers from 500 birds. You extract DNA from the feathers and determine the genotype of the birds at the plumage gene. You genotype 245 white birds and you find that they are all homozygous for the m allele. You genotype 255 brown birds and find that 190 of them are homozygous for the M allele and 65 are heterozygous (Mm).

b. Given this genotype data, what is the frequency of the M allele?

c. Given the what you know about expected and observed genotype frequencies in this group, do you expect that the null hypothesis of Hardy-Weinberg Equilibrium holds true? If not, what evolutionary phenomenon might explain this discrepancy?

beigesalmon41

Q1. Which of the following statements is true about the disease Kuru?
Kuru is caused by a virus, which is contracted by eating human brain material.
Kuru is caused by a prion (PrP), which is contracted by eating human brain material.
Kuru is caused by a recessive allele for PrP; if a person has two copies, he or she will develop Kuru.
Kuru is caused by a dominant allele for PrP; if a person has two copies, he or she will develop Kuru.
Kuru is caused by having one copy of the dominant allele and one copy of the recessive allele for PrP.

Q2. True or false: One can calculate the frequency of alleles in a population if the genotypes of the members of the population are known.

True False

Q3. The Hardy-Weinberg equation is p2 + 2pq + q2. In this equation, q2 stands for the frequency of ____________ in a population.

The recessive allele O

ne of the homozygous genotypes

The dominant allele

Heterozygous genotype

Q4. Which of the following descriptions best fits the relationship between the terms gene, allele, locus, and chromosome?

Alleles are different forms of a gene, which can be found at a locus on a chromosome.

Genes are made up of chromosomes, which can be found at a locus on an allele.

Chromosomes are different forms of a gene, which can be found at an allele on a locus.

A locus is made up of alleles, which can be found at a gene on a chromosome.

Q5. Mead and his colleagues proposed a hypothesis for the apparent heterozygote advantage for the PrP locus. What did they suggest as the basis for the high presence of both alleles?
History of cannibalism.
Protection from malaria.
Protection against plague.
They did not propose a heterozygotic advantage for the PrP locus.

Q7. A frog population has two alleles for skin color at the following relative frequencies: Allele SC1= 0.8, Allele SC2 = 0.2. Allele SC2 is:
Dominant
Recessive
Co-dominant
Impossible to determine dominance from the information given.

Q8. A bird population has two alleles for feather color at the following relative frequencies: Allele FC1 = 0.5, Allele FC2 = 0.5. Allele FC1 is:
Dominant
Recessive
Co-dominant
Impossible to determine dominance from the information given.

Q9. Use the following information for both questions 9 and 10: You encounter a few populations of millipedes with variation in skin color. Genotype can be inferred from coloration: CC millipedes are black, Cc millipedes are brown, and cc millipedes are yellow. [You can launch a calculator byclicking here.]

If one millipede population has 60 black individuals, 20 brown individuals, and 20 yellow individuals, what is the relative frequency of allele C in that population?

0.5
0.6
0.7
0.8
Impossible to calculate from the information given.

Q10. If another millipede population's allele frequencies are 0.5 for C and 0.5 for c, what is the expected frequency of the cc genotype in the population, if the population is in Hardy-Weinberg equilibrium?
0.125
0.25
0.5
1.0
Impossible to calculate from the information given.

greenskunk262

CAS BI 107 Lecture Notes - Lecture 3: Genotype Frequency, Allele Frequency, Heterozygote Advantage

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