AP Biology : Evolution and Genetics

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #12 : Population Genetics

A population of beetles exists in which black coloration is dominant to white. If there are 36 white beetles in a population of 100 beetles, what is the dominant allele frequency?

Possible Answers:

Unable to determine from the given information

Correct answer:

Explanation:

There are multiple ways to solve this problem, but the easiest is to use the Hardy-Weinberg equations:

We are told the frequency of white beetles in the population. Using this value, we can find the recessive allele frequency. is equivalent to the homozygous recessive genotype frequency.

Use this value to solve for the dominant allele frequency.

Example Question #14 : Understanding Hardy Weinberg Assumptions And Calculations

In a given population of snails, spiral shells are dominant to round shells. If 36% of the population is homozygous for the spiral shell allele, what percentage of the population is heterozygous?

Possible Answers:

Correct answer:

Explanation:

We can use the Hardy-Weinberg equations to solve this problem.

We know that spiral shells are dominant, and that 36% of the population is homozygous for the spiral allele. This tells us that 36% of the population is homozygous dominant. The  term corresponds to the homozygous dominant percentage.

 is the dominant allele frequency. Now we can solve for , the recessive allele frequency.

The term  will give us the frequency of heterozygotes.

48% of the population is heterozygous.

Example Question #11 : Population Genetics

If four percent of the population is homozygous recessive for the trait that carries dimples (recessive), what is the fractional frequency of the dominant allele?

Possible Answers:

Correct answer:

Explanation:

Using the Hardy-Weinberg law to solve for allele frequency in populations, you can solve for the answer using the following two equations.

p is the fractional frequency of the dominant allele, q is the fractional frequency of the recessive allele, and q2 is the fraction of the population that is homozygous recessive. q2 is given in the question to be 0.04 (or 4%).

Example Question #11 : Population Genetics

Which of the following is not a Hardy-Weinberg assumption?

Possible Answers:

Population size is large enough to prevent random drift

There is nonrandom mating

There is no natural selection

There is no migration

There is no mutation

Correct answer:

There is nonrandom mating

Explanation:

Random mating is a Hardy-Weinberg assumption, not nonrandom. The remaining answer choices are all standard assumptions for Hardy-Weinberg equilibrium. Nonrandom mating would allow certain alleles to be preferentially passed down over generations. 

Example Question #21 : Understanding Hardy Weinberg Assumptions And Calculations

Which of the following are assumptions made by the Hardy-Weinberg principle?

Possible Answers:

Large population size

No migration, mutation, and selection

Random mating and sexual reproduction

All of these

Correct answer:

All of these

Explanation:

The Hardy-Weinberg principle is a theory that describes how allele frequencies may change within a population absent of evolutionary mechanisms. The theorem is based on certain assumptions regarding the population in question. These assumptions include random mating, large population size, sexual reproduction, and the absence of migration, mutation and selection. It is exceedingly rare for all the Hardy-Weinberg assumptions to be met in nature, but this theory is a tool used to study allele frequencies within populations. 

Example Question #22 : Understanding Hardy Weinberg Assumptions And Calculations

In the Hardy-Weinberg theorem,  refers to what?

Possible Answers:

The frequency of the dominant allele

The frequency of the homozygous recessive genotype

The frequency of the homozygous dominant genotype

The frequency of the recessive allele

Correct answer:

The frequency of the dominant allele

Explanation:

In the Hardy-Weinberg theory, the two equations used are:

Here,  refers to the frequency of the dominant allele and  refers to the frequency of the recessive allele. Subsequently,  refers to the frequency of the homozygous dominant genotype,  refers to the frequency of the homozygous recessive genotype, and  refers to the frequency of the heterozygous genotype.

Example Question #22 : Understanding Hardy Weinberg Assumptions And Calculations

Which of the following are deviations from the Hardy-Weinberg equilibrium?

Possible Answers:

Migration only

Random mating only

Mutation only

Mutation and migration

Random mating and mutation

Correct answer:

Mutation and migration

Explanation:

In Hardy-Weinberg equilibrium, deviations are violations of the assumptions of the Hardy-Weinberg theory. The assumptions of the Hardy-Weinberg theoru include random mating, large population size, sexual reproduction, and the absence of migration, mutation and selection. Therefore, deviations from the Hardy-Weinberg equilibrium from the options are mutation and migration.

Example Question #141 : Evolution And Genetics

What is the best explanation for a population being described as an evolutionary unit?

Possible Answers:

Genetic changes occur only in populations

Natural selection only involves individuals, not populations

Natural selection only occurs across species

A population's gene pool remains the same throughout time

Populations can evolve, not individuals

Correct answer:

Populations can evolve, not individuals

Explanation:

The genetic make up of populations can be measured over time. While genetic changes only occur at the individual level, it is only populations that evolve since genetic changes take many generations to develop into phenotypic changes that may be observed as changing allele frequencies over time.

Example Question #144 : Evolution And Genetics

Which of the following is not an assumption of Hardy-Weinberg equilibrium?

Possible Answers:

Mating is random

Mutations do not occur

No traits have an influence on natural selection

There is no flow of new genes from an outside population

The population is small

Correct answer:

The population is small

Explanation:

The five answers listed are all assumptions of Hardy-Weinberg equilibrium except for the population being small. In fact, the population must be large so that random chance during mating and death will not result in certain alleles changing their proportion in the population.

Example Question #25 : Population Genetics

In a population of rabbits, the dominant allele for eye color is black and the recessive allele for eye color is brown. If 9% of the population is brown eyed, what percent of the population is heterozygous for eye color?

Possible Answers:

Correct answer:

Explanation:

In order to answer this question, you must remember the Hardy-Weinberg equations. 

In the above equations,  stands for the frequency of the dominant allele and  stands for the frequency of the recessive allele. 

It is also important to realize that  stands for the homozygous dominant population,  stands for the homozygous recessive population, and  stands for the heterozygous population. 

We are told that 9% of the population is brown eyed, or homozygous recessive. Let's solve for .

Now let's solve for .

The question asks for the percent of the population that is heterozygous. In order to do this, we look at the first equation and plug in known values.

Thus, our answer is 42%.

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