Question 1

A locus has two alleles.The frequency of heterozygotes in a population at Hardy-Weinberg equilibrium is 0.32.What is the frequency of the more common of the two alleles?

Accepted Answer

The frequency of heterozygotes in a Hardy-Weinberg population is given by 2pq, where p and q are the frequencies of the two alleles. If 2pq = 0.32, then pq = 0.16. Since p + q = 1, we can solve for p or q. Assuming p is the more common allele, p = 1 - q. Substituting pq = 0.16, we find that p = 0.8, making it the frequency of the more common allele.

Question 2

In a population of 800 wolves, 320 are CC and 360 are Cc for a locus with two alleles.Which statement is true?

Accepted Answer

The frequency of an allele is the proportion of that allele in the total number of alleles in the population.

Here, the total number of alleles is 2 * 800 = 1600 (because each individual has two alleles).

The frequency of C allele = (320 * 2 + 360) / 1600 = 1,000 / 1,600 = 0.625.

Therefore, the correct answer is A, the frequency of the C allele is 0.625.

Question 3

You discover a population of guppies and find it to be at Hardy-Weinberg equilibrium with respect to the S locus.Suppose there are two alleles at this locus and that the frequency of the s allele is 0.4.Of the individuals that carry at least one s allele, what fraction are homozygotes?

Accepted Answer

In Hardy-Weinberg equilibrium, the frequency of homozygotes for the recessive allele is q^2, where q is the frequency of the recessive allele. 
Here, q = 0.4, so q^2 = 0.16. Therefore, 16% of the individuals carrying at least one s allele are homozygotes. 
To convert this into a fraction, we can write 16% as 1/6, which corresponds to answer choice C.

Question 4

Three populations of mustard plants are sampled for variation at the F locus.Population A is 20 percent FF, 60 percent Ff, and 20 percent ff.Population B is 63 percent FF, 34 percent Ff, and 3 percent ff.Population C is 35 percent FF, 30 percent Ff, and 35 percent ff.Which population(s) show(s) a heterozygote deficiency?

Accepted Answer

The answer of Three populations of mustard plants are sampled...

Question 5

In a haploid bacterium, 720 of 900 individuals have the c1 allele.What is the frequency of the c1allele?

Accepted Answer

The frequency of the c1 allele can be calculated by dividing the number of individuals with the c1 allele by the total number of individuals in the population.

Frequency of c1 allele = Number of individuals with c1 allele / Total number of individuals

In this case, the number of individuals with the c1 allele is given as 720 out of 900 individuals.

Frequency of c1 allele = 720/900 = 0.8

Therefore, the frequency of the c1 allele is 0.8 or 80%. The best choice is option C.

Question 6

Calculate the frequency of homozygotes for an allele at a locus in a population at Hardy-Weinberg equilibrium if the frequency of the allele is 0.15.

Accepted Answer

The frequency of homozygotes for an allele (q) in a population at Hardy-Weinberg equilibrium is calculated as q^2. Given the allele frequency is 0.15 (q = 0.15), the frequency of homozygotes is 0.15^2 = 0.0225.

Question 7

Suppose there are two alleles at a locus and that the locus is at Hardy-Weinberg equilibrium.If the frequency of one allele is r, what is the frequency of the heterozygotes?

Accepted Answer

The frequency of heterozygotes in a population at Hardy-Weinberg equilibrium is given by 2pq, where p and q are the frequencies of the two alleles. If the frequency of one allele is r, then the frequency of the other allele is 1 - r. Therefore, the frequency of the heterozygotes is 2r × (1 - r).

Question 8

Deviations from Hardy-Weinberg

Accepted Answer

Deviations from Hardy-Weinberg equilibrium occur when evolutionary forces such as mutation, selection, genetic drift, migration, and non-random mating are operating on the population. This can result in changes in allele frequencies and genotypic frequencies, which can deviate from the expected values under Hardy-Weinberg equilibrium.

Question 9

A population of ocotillo plants has four alleles at the Dopa locus, with allelic frequencies of 0.38, 0.32, 0.19, and 0.11, and the genotype frequencies are roughly consistent with the Hardy-Weinberg equilibrium.This is a description of the genetic _______ of the population.

Accepted Answer

The genetic structure of a population refers to the distribution of alleles and genotypes, which is described here by the allelic and genotype frequencies.

Question 10

Which of the following statements about the Hardy-Weinberg equilibrium is false?

Accepted Answer

The Hardy-Weinberg equilibrium assumes random mating, meaning that individuals do not prefer to mate with individuals with certain genotypes. Therefore, statement D is false.

Question 11

An allele in a population of trout has a frequency of 0.37.In 300 trout, how many copies of the allele are present?

Accepted Answer

Each trout has two sets of chromosomes, meaning there are 600 alleles in total (300 trout x 2). The number of copies of the allele is 0.37 x 600 = 222.

Question 12

The FY3 gene plays a role in immune responses in flies.In one population, there are two alleles, and the frequency of one allele is 0.8.If the population is at Hardy-Weinberg equilibrium, how many homozygotes for the more common allele should we observe in a sample of 250 individuals?

Accepted Answer

The frequency of the more common allele is 0.8, so the frequency of homozygotes for this allele (p^2 in Hardy-Weinberg equation) is 0.8^2 = 0.64. In a sample of 250 individuals, the expected number of such homozygotes is 0.64 * 250 = 160.

Question 13

In a population of 600 moose, 30 percent of the individuals are homozygous for an allele and 45 percent are heterozygotes.How many copies of the allele are present in the population?

Accepted Answer

In this population, 30% are homozygous for the allele, meaning they have two copies each, and 45% are heterozygotes, meaning they have one copy each. For 600 moose, 30% homozygous equals 180 moose (600 * 0.30), each contributing 2 alleles for a total of 360 alleles. 45% heterozygous equals 270 moose (600 * 0.45), each contributing 1 allele for a total of 270 alleles. Adding these together gives 360 + 270 = 630 alleles in the population.

Question 14

By definition, a population that is fixed for an allele _______ at that locus.

Accepted Answer

A population that is fixed for an allele means that all individuals in that population have the same allele at that locus. This is called monomorphism. Therefore, the correct choice is B.

Question 15

A population of 600 horses has 70 individuals that are AA and 160 that are Aa at a locus involved in immune response.Assuming that these are the only alleles at that locus, what is the frequency of a?

Accepted Answer

To find the frequency of allele a, first, calculate the total number of alleles for the locus in the population, which is 2 times the population size (since each individual has two alleles for each locus), giving 2 * 600 = 1200 alleles. The number of a alleles can be calculated by adding twice the number of aa individuals (but there are none explicitly mentioned, assuming AA and Aa are the only genotypes, aa is inferred) to the number of Aa individuals, since each Aa individual contributes one a allele. However, since no aa individuals are mentioned, we focus on Aa and AA. The total number of A alleles is 2*70 (from AA) + 160 (from Aa), and the remainder must be a alleles. Given 70 AA individuals contribute 0 a alleles, and 160 Aa individuals contribute 160 a alleles. If there were aa individuals, they would contribute 2 alleles each, but since the total number of individuals is accounted for with AA and Aa, we infer the rest of the alleles. The calculation for the frequency of a is then based on the total number of a alleles divided by the total number of alleles. The total number of a alleles is 1200 - (2*70 + 160) = 1200 - 300 = 900 a alleles. Therefore, the frequency of a is 900 / 1200 = 0.75.

Question 16

An allele in a population of mockingbirds has a frequency of 0.3.In a population of 600, how many copies of the allele are present?

Accepted Answer

Frequency of the allele = 0.3
Total population = 600
Number of copies of the allele = Frequency x Total population
= 0.3 x 600
= 180 + 180 (from the other allele)
= 360 
Therefore, the correct answer is choice C.

Question 17

A sample of 200 individuals from a population of blister beetles has 105 individuals that are GG for the G locus, 70 that are Gg, and 25 that are gg.This means that the population

Accepted Answer

The answer of A sample of 200 individuals from a...

Question 18

The FY3 gene plays a role in immune responses in flies.In one population, there are two alleles, and the frequency of one allele is 0.6.If the population is at Hardy-Weinberg equilibrium, what is the frequency of heterozygotes?

Accepted Answer

The frequency of heterozygotes in a population at Hardy-Weinberg equilibrium can be calculated using the equation 2pq, where p is the frequency of one allele and q is the frequency of the other allele. If the frequency of one allele (p) is 0.6, then the frequency of the other allele (q) is 1 - 0.6 = 0.4. Therefore, the frequency of heterozygotes is 2(0.6)(0.4) = 0.48.

Question 19

If the frequency of the A3 allele of a creatine phosphatase locus in a population of lions is 0.4, how many copies of that allele should we expect to see in a population of 500 lions?

Accepted Answer

The frequency of an allele is the number of copies of that allele in a population divided by the total number of alleles in the population. In this case, the frequency of the A3 allele is 0.4, which means that there are 400 copies of the A3 allele in a population of 1000 lions. Therefore, we would expect to see 200 copies of the A3 allele in a population of 500 lions.

Question 20

Which type of selection is most likely to result in an evolutionary trend?

Accepted Answer

Directional selection occurs when individuals at one end of the phenotypic spectrum have increased reproductive success. This results in a shift in the average phenotype in a particular direction, leading to an evolutionary trend. Therefore, directional selection is the type of selection most likely to result in an evolutionary trend.

Quiz 20: Mechanisms of Evolution