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Biology 3593B Study Guide - Quiz Guide: Population Genetics, Genotype Frequency, Allele Frequency

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20 May 2020
School
Western University
Department
Biology
Course
Biology 3593B
Professor
P. McDonald

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Document Summary

Find the number of individuals with certain phenotypes (after which, we assume the genotype) Calculate the number of dominant and recessive alleles, using number of individuals (for homozygotes x2, for heterozygotes the same number) Calculate allele frequency (number of dominant or recessive alleles / total number of alleles) *in rare traits p is approximate to 1, hence frequency of carrier for such trait = 2q: aim of population genetics and its applications in medicine. Population = a group of genetically related individuals living close enough to be able to interbreed and produce fertile offspring. Population genetics studies distribution of genes in populations & factors that maintain or change the frequency of genes and genotypes from generation to generation. It explains why in large populations allele frequencies do not change from generation to generation, but also how genotype frequencies are determined by the frequencies of alleles: general statement of hardy-weinberg law.

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Related Questions

Part A

In humans, individuals may or may not have a widow’s peak. This trait is controlled by genes at a single locus, with the allele for having a widow’s peak dominant to the allele for not having one. A population of humans is sampled; 59 have a widow’s peak and 44 do not. 25 of the people with a widow’s peak are homozygous dominant. What are the frequencies of the dominant and recessive alleles observed in this sample?

p = _____

q = _____

Part B

In a species of corn, individuals have either narrow or wide corn cobs. This trait is controlled by genes at a single locus, with the narrow cob allele dominant to the wide cob allele. A farmer counts 74 narrow cob and 113 wide cob plants in a field. Of the narrow cob plants, 28 are homozygous dominant. What are the frequencies of the dominant and recessive alleles observed in this sample?

p = _____

q = _____

Part C

In a population of peas, the frequency of the dominant allele for a purple flower is 0.61 and the frequency of the recessive allele for a white flower is 0.39. What would the genotypic frequencies be if the population is in equilibrium?

_____ = Frequency of homozygous dominant individuals

_____ = Frequency of heterozygous individuals

_____ = Frequency of homozygous recessive individuals

How many individuals would you expect of each genotype in a population of 500 peas?

_____ = Number of homozygous dominant individuals

_____ = Number of heterozygous individuals

_____ = Number of homozygous recessive individuals

Part D

In mice, a mahogany coat color allele is dominant over the tan coat color allele. In a population of mice, the frequency of the allele for mahogany coat color is 0.19 and the frequency of the allele for tan coat color is 0.81. What would the genotypic frequencies be if the population is in equilibrium?

_____ = Frequency of homozygous dominant individuals

_____ = Frequency of heterozygous individuals

_____ = Frequency of homozygous recessive individuals

How many individuals would you expect of each genotype in a population of 100 mice?

_____ = Number of homozygous dominant individuals

_____ = Number of heterozygous individuals

_____ = Number of homozygous recessive individuals

Part E

In humans, the free earlobe allele is dominant over the attached ear lobe allele. In a population of humans, the frequency of the allele for free earlobes is 0.42 and the frequency of the allele for attached earlobes is 0.58. What would the genotypic frequencies be if the population is in equilibrium?

_____ = Frequency of homozygous dominant individuals

_____ = Frequency of heterozygous individuals

_____ = Frequency of homozygous recessive individuals

How many individuals would you expect of each genotype in a population of 25 humans?

_____ = Number of homozygous dominant individuals

_____ = Number of heterozygous individuals

_____ = Number of homozygous recessive individuals

Rank the following terms in increasing order of scale accordingto your knowledge of their definitions:

-Locus
-Allele
-Chromosome
-Gene

If 16% of a population expressed a recessive trait, whatpercentage of the gene pool is the dominant allele?

Consider a population of Peach-faced lovebirds where:

65% of all gametes carry a dominant allele (F)for regular plumage (feather colors).

The remaining 35% carry the recessive allele(f) for a plumage with white.

When two heterozygous (Ff) individuals breed,we expect the genotype Ff to account for_____% ofthe new generation.

In the case of a species of sea lions displaying assortativemating (where individuals prefer to mate with individuals that looklike them), the conditions for Hardy-Weinberg Equilibrium are stillmet and supported (T or F)

If 90% of the alleles in a population are dominant, what is theratio of genotypes?


What are genes comprised of?


In the Hardy-Weinberg equation, what does 2pq denote?

Without strong natural selection, recessive alleles willinevitable disappear from a population T or F


If the proportion of sickle-cell sufferers(HbS-HbS homozygotes) in a population is 0.04,according to the Hardy-Weinberg equation, what is the proportion ofsickle-cell carriers (HbS-HbA heterozygotes) in thatpopulation?






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.