BI111 Chapter Notes - Chapter 67: Allele Frequency, Genotype Frequency, Genetic Drift

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23 Jan 2019

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A population is made up of a group of interacting and interbreeding members of the same species. Each individual within a population has its own alleles for each gene (its genotype), and the frequencies of alleles in a population can vary for a number of reasons, including mutation, recombination, drift, and selection. Determining whether a gene is evolving in a population. An organism"s traits are the product of evolution, heavily influenced by interactions between individuals, their genes, and environment. Traits are properties controlled by different alleles of genes (genotypes) and expressed as characteristics (phenotypes) To establish whether evolution is occurring, it is necessary to measure allele frequency and genotype frequency. Every individual within a population has a genotype and a resulting phenotype. A genotype is the genetic (or allelic) makeup of an individual and can be examined for each specific character. For any gene, there are many different alternative forms, known as alleles.

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Q3.15. Which of thefollowing statements about genes and alleles is TRUE?

a.)Quantitative traits are each determined by a single gene thathas a small number of alleles.

b.)When a gene has two alleles, the allele frequencies in apopulation move toward equilibrium values of 0.5 for eachallele.

c.)All else being equal, alleles associated with higherreproductive success increase in frequency.

d.)If the frequency of an allele in a population has changed,then natural selection has necessarily occurred.

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Hemoglobin and Fitness Instructions Directions: Neutral Evolution

1. Obtain 20 beans of two different colors (e.g., white and red). Count out 16 white and 4 red beans. The white beans represent the Hn allele and the red beans represent the Hs allele. This is the genetic makeup of your starting population. (Note: You can use any objects that can readily be categorized into two groups, such as coins, colored rocks, or paper clips.)

2.Calculate the frequency of both alleles [f(Hn) and f(Hs)] and record them in Table 1. In our experiment frequency is a measure of how many copies of a given allele exist in the gene pool (i.e., a proportion). Use decimal values. â¨

3.Arrange the beans into pairs. These pairs represent the genotype of each of 10 individuals in the population. Record the number of individuals with each genotype [f(Hn Hn), f(Hn Hs), and f(HsHs)] in Table 1. â¨

4.Now imagine that the individuals are living and reproducing with each individual reproducing at the same rate (i.e., all individuals produce two copies of each of their alleles into the next generation). Obtain enough beans to represent the next generationâ the offspring generationâand then let the parental generation âdieâ. â¨

5.Calculate the frequency of each allele in the offspring generation and record it in Table 1. â¨

Answer the questions that follow in Table 1. â¨

Table 1

	f(HnHn)	f(HnHs)	f(HsHs)	f(Hn)	f(Hs)
oiginal generation
offspring generation

Answer the following questions to help you understand the exercise:

What happened to the frequency of the common allele? â¨

What happened to the frequency of the rare allele? â¨

What happened to the frequency of the common and rare alleles when the starting frequencies were different from yours

What happens to allele frequencies from one generation to the next if there are no evolutionary forces acting on the population? â¨

greyotter669

Indicate the effect of this condition of the Hardy-Weinbergprinciple on genotype and allele frequencies: assortativemating
a.alters genotype and allele frequencies
b.alters genotype only
c.alters allele frequency only
d.does not alter genotype or allele frequency

Polydactylism (possessing more than five fingers per hand) withinthe Amish population in Pennsylvania is considered an example offounder effect. This is because the frequency of polydactylismamong the Amish in Pennsylvania is identical to its frequency amongthe Amish population in Germany.
a.true.
b.false

A population of bacteria is in Hardy-Weinberg equilibrium. However,through repeated exposure to an antibiotic, the frequency of therecessive allele is rapidly increasing. What is the most likelyexplanation for this response? The recessive allele is responsiblefor susceptibility of the bacteria to the antibiotic.
a.The dominant allele is responsible for susceptibility of thebacteria to the antibiotic.
b.The recessive allele is responsible for resistance of thebacteria to the antibiotic.
c.The population is experiencing gene flow.
d.The population is experiencing disruptive selection.

Biotic environments that influence natural selection includes allbut which of the following?
a.competition
b.predation
c.parasitism
d.weather
e.disease

Why does the malaria disease persist in the human population?
a.Too few humans have died of malaria to end the disease.
b.Multiple phenotypes survive in a balanced polymorphism.
c.Malaria is a recessive disease and few humans are eversick.
d.Humans are protected from the malaria parasite.
e.The disease is under stabilizing selection.

In random mating,;

A.individuals choose the most attractive mate.
B.there is no influence on mate choice.
C.breeding occurs between two different species.
D.breeding occurs between two different subspecies.
E.fertile offspring are not produced.

A fraction of the original green frog population survives toreproduce and generate the new population. If the survivors of theoriginal population survived by chance, then this event is anexample of
A.natural selection.
B.genetic drift.
C.founder effect.
D.industrial melanism.

Which of the following is most likely an example of a foundereffect event?
A.A random small group of a bird population migrates to an islandand then returns to breed.

B.A random large group of a bird population migrates to an islandand then returns to breed.

C.A selected small group of a bird population migrates to an islandand then returns to breed.

D.A random small group of a bird population migrates to an islandand does not return to breed.

E.A random large group of a bird population migrates to an islandand does not return to breed.

Microevolution is not influenced by which of the following?

A.mutation
B.random mating
C.gene flow
D.natural selection
E.genetic drift

BI111 Chapter Notes - Chapter 67: Allele Frequency, Genotype Frequency, Genetic Drift

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