Evolution and Genetics
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AP Biology › Evolution and Genetics
A population of snails is in Hardy-Weinberg equilibrium. The snails come in two different colors: red, the dominant phenotype, and white, the recessive phenotype. There are sixteen homozygous dominant, forty-eight heterozygous, and thirty-six homozygous recessive snails.
What are the allele frequencies for this population?
Explanation
We can solve this question using the Hardy-Weinberg equations:
In the second equation, 
We can find the values of 
A population of snails is originally in Hardy-Weinberg equilibrium. The snails come in two different colors: red, the dominant phenotype, and white, the recessive phenotype. The original population has a dominant allele frequency of 
What is the recessive allele frequency after the introduction of this predator?
Explanation
Most of the information in the question is actually superfluous because we are given the final dominant allele frequency. The dominant allele frequency corresponds to the variable 
The question tells us that the dominant allele frequency after introduction of the predator is 
A population of snails is in Hardy-Weinberg equilibrium. The snails come in two different colors: red, the dominant phenotype, and white, the recessive phenotype. The population consists of sixty-four red snails and thirty-six white snails.
Assuming that the population is in Hardy-Weinberg equilibrium, what is the value of 
Explanation
We can solve this question using the Hardy-Weinberg equations:
The question tells us the number of dominant red snails and the number of recessive white snails. Using these values, we can find the frequency of the recessive phenotype.
From here, take the square root to find the value of 
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?
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%).
Which is true of a pea plant with rounded pods and alleles Rr?
The phenotype is Rr and the genotype is rounded pods
The genotype is Rr and the phenotype is rounded pods
The F1 generation will only have rounded pods
The F2 generation will only have rounded pods
Explanation
The genotype describes the genetic makeup or alleles of the individual, while the phenotype describes the physical characteristic of the individual.
Which of the following concepts was not discovered by the scientist Gregor Mendel?
The likelihood of alleles for different traits being inherited together is based on how close together those alleles are on the chromosome.
Organisms have two alleles for each trait, one allele from each parent.
The traits of organisms are determined by factors inherited from their parents.
Alleles for different traits are passed down from parents to offspring independently from each other.
The effects of recessive alleles are masked by the presence of dominant alleles.
Explanation
The overall idea that Mendel was studying was that organisms have two alleles per trait, and that each parent passes down one allele. The other answers refer to Mendel’s laws: the Law of Segregation, the Law of Independent Assortment, and the Law of Dominance. Mendel was unaware of genetic linkage, which is an exception to the Law of Independent Assortment. We know this to be true because chromosomes and DNA had not yet been discovered in his time.
The sum of all genetic alleles in a population is the .
gene pool
gene frequency
gene supply
gene resources
gene stock
Explanation
A population is composed of numerous individuals, each carrying a common set of genes with a unique combination of genetic alleles. The gene pool is the sum of all of these alleles.
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?
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%).
A population of snails is originally in Hardy-Weinberg equilibrium. The snails come in two different colors: red, the dominant phenotype, and white, the recessive phenotype. The original population has a dominant allele frequency of
What is the recessive allele frequency after the introduction of this predator?
Explanation
Most of the information in the question is actually superfluous because we are given the final dominant allele frequency. The dominant allele frequency corresponds to the variable
The question tells us that the dominant allele frequency after introduction of the predator is
Which of the following is a Hardy-Weinberg assumption?
Random mating
Natural selection is in operation
High rate of mutation
Gene flow between populations
Explanation
Random mating is one of the five Hardy-Weinberg assumptions that help maintain equilibrium. If random mating occurs, in tandem with the other assumptions, we can reasonably assume that there will not be a shift in allele frequencies or distributions.
The other Hardy-Weinberg assumptions are that natural selection does not occur, mutation does not occur, genetic drift (gene flow) does not occur, and that the population size is large.