Question 1

The percentage of different colored water boatmen eaten by fish were graphed relative to the frequency of that color in the population.Based on the graph,a population of water boatmen would ________

Accepted Answer

The answer of  The percentage of different colored water...

Question 2

In a large population of randomly reproducing rabbits,a recessive allele r comprises 80% of the alleles for a gene.What percentage of the rabbits would you expect to have the recessive phenotype?

Accepted Answer

According to the Hardy-Weinberg principle, the frequency of homozygous recessive individuals (rr) can be calculated using the equation p^2 + 2pq + q^2 = 1, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. If the recessive allele comprises 80% of the alleles, then q = 0.8 and p = 0.2. Therefore, the frequency of homozygous recessive individuals is q^2 = 0.64 or 64%.

Question 3

The recessive phenotype of a trait occurs in 16% of a population.What is the frequency of the dominant allele?

Accepted Answer

The frequency of the recessive phenotype (q^2) is 0.16. To find the frequency of the recessive allele (q), take the square root of 0.16, which is 0.4. The frequency of the dominant allele (p) is 1 - q, which is 1 - 0.4 = 0.6 or 60%.

Question 4

In disruptive selection,over time

Accepted Answer

Disruptive selection favors individuals at both extremes of the phenotypic range, leading to a population that diverges into two distinct groups, such as those with larger and smaller beak sizes, rather than favoring a single median phenotype.

Question 5

Coloration in the peppered moth (Biston betularia)is determined by a single gene with two alleles showing complete dominance.Dark moths are homozygous dominant or heterozygous for the gene,light moths are homozygous recessive.In a sample of 100 moths,you determine that 64 of the moths are dark.According to the Hardy-Weinberg rule,the expected frequency of the dominant allele is ________.

Accepted Answer

The frequency of the dominant allele can be calculated using the Hardy-Weinberg principle. Given that 64% of the moths are dark (homozygous dominant or heterozygous), and assuming the population is in Hardy-Weinberg equilibrium, we can use the square root of the dominant phenotype frequency to estimate the dominant allele frequency. However, the correct approach involves understanding that the frequency of the homozygous recessive genotype (light moths) can be used to calculate allele frequencies. If 64 moths are dark, then 36 moths are light (100 - 64 = 36), and since light moths are homozygous recessive, the frequency of the recessive allele (q) is the square root of 0.36 (q^2 = 0.36), which gives q = 0.6. The frequency of the dominant allele (p) is then 1 - q = 1 - 0.6 = 0.4. Therefore, the expected frequency of the dominant allele is 0.4.

Question 6

In some instances environmental change causes a situation where one phenotype is favored for a period of time,and then a different phenotype is favored.This oscillating selection causes

Accepted Answer

Oscillating selection maintains genetic variation because different phenotypes are favored at different times. This allows for the persistence of multiple alleles in a population rather than the fixation of one allele over time.

Question 7

An insect population that becomes resistant to a commonly used insecticide is an example of ________.

Accepted Answer

The development of insect populations that become resistant to a commonly used insecticide is an example of natural selection. In this situation, insects that have genetic variations that make them less susceptible to the insecticide survive and reproduce, passing on their resistant traits to their offspring. Over time, the resistant population becomes dominant, and the susceptibility of the insect population to the insecticide decreases.

Question 8

________ would produce the smallest evolutionary change in a given period of time in a population of birds.

Accepted Answer

The answer of ________ would produce the smallest evolutionary change...

Question 9

A fur color gene in rabbits has a white dominant (W)and brown recessive allele (w).The environment changes suddenly and none of the white rabbits survive.In a population of 10,000 rabbits the initial frequency of W in the pool was 0.7.How many generations would be required to eliminate all W alleles from the population? Assume that there is no mutation and the population meets all other Hardy-Weinberg conditions.

Accepted Answer

The answer of A fur color gene in rabbits has...

Question 10

A human autosomal recessive trait appears in 1 in 100 births.What percent of people are homozygous dominant for this trait?

Accepted Answer

Since the trait is autosomal recessive, the only way for someone to be homozygous dominant is if both parents are also homozygous dominant. Since the trait appears in 1 in 100 births, the frequency of the homozygous dominant genotype would be much lower. The frequency of the homozygous recessive genotype (affected individuals) is q2 = 0.01, so q (the frequency of the recessive allele) is sqrt(0.01) = 0.1.

Using the equation p + q = 1, where p is the frequency of the dominant allele:

p + 0.1 = 1

p = 0.9

Therefore, the frequency of the homozygous dominant genotype (p2) would be:

p2 = (0.9)2 = 0.81 or 81%

Question 11

Antigens on red blood cells are hereditary traits that allow blood to be typed in different ways.One system is based on a gene with two alleles,M and N.If the frequency of the M allele in a population is 0.4,then according to the Hardy-Weinberg rule,the expected frequency of the heterozygous MN genotype is ________.

Accepted Answer

According to the Hardy-Weinberg rule, the frequency of the MN genotype can be calculated using the equation: 2pq, where p is the frequency of the M allele and q is the frequency of the N allele (p + q = 1). Here, p = 0.4 and q = 0.6 (1 - 0.4). Therefore, 2pq = 2(0.4)(0.6) = 0.48 or 48%. Thus, the expected frequency of the heterozygous MN genotype is 0.48 or 48%. The closest answer choice is D) 0.48.

Question 12

People homozygous for the sickle-cell anemia allele develop a life threatening disease,while those homozygous for the normal allele are at the highest risk of dying from malaria.Carriers have some resistance to malaria,but do not develop sickle cell anemia.This is an example of ________

Accepted Answer

This is an example of heterozygote advantage, where carriers (heterozygotes) have a selective advantage over both homozygotes (sickle-cell anemia and normal) in certain environments (areas with a high prevalence of malaria).

Question 13

During a drought on the Galapagos islands,finches with larger beaks were able to crack the large tough seeds produced by plants that survived the dry conditions.This is an example of ________.

Accepted Answer

The fact that finches with larger beaks had a higher survival rate during the drought indicates that natural selection was favoring individuals with this trait. Directional selection occurs when natural selection favors individuals at one extreme of a trait distribution, as was the case here with larger beaks.

Question 14

The California populations of the Northern elephant seal are descendants from a very small population of seals that was overhunted in the 1890s.Heterozygosity in this population would be expected to be ________ due to ________.

Accepted Answer

A bottleneck effect occurs when a population's size is significantly reduced for at least one generation, leading to a loss of genetic variation. Since the Northern elephant seal populations in California are descendants from a very small population due to overhunting, they would have gone through a bottleneck effect, resulting in reduced genetic diversity or heterozygosity.

Question 15

You are studying a population of geese in which there are two color phases,brown and gray.Color in this species is controlled by a single gene,with brown dominant to gray.A random sample of 250 geese shows that 210 are brown.What percentage of the brown geese are heterozygous? (Assume that the population is in Hardy-Weinberg equilibrium.)

Accepted Answer

To find the percentage of heterozygous brown geese, first calculate the allele frequencies. Let p be the frequency of the brown allele and q be the frequency of the gray allele. Since 210 out of 250 geese are brown, 40 are gray, which are homozygous recessive (q^2). Thus, q^2 = 40/250 = 0.16, so q = 0.4. Therefore, p = 1 - q = 0.6. The frequency of heterozygous brown geese is 2pq = 2(0.6)(0.4) = 0.48. Since 210 geese are brown, 0.48 * 250 = 120 are heterozygous. The percentage of heterozygous brown geese is (120/210) * 100% = 57%.

Question 16

________ could not be involved in gene flow.

Accepted Answer

Disassortative mating within a population would result in individuals mating with those who are dissimilar to them, which would decrease gene flow within the population. Wind-blown pollen, gametes and zygotes dispersed by ocean currents, and hybridization between neighboring populations would all contribute to gene flow.

Question 17

The disease,sickle-cell anemia is common in malaria-infested areas because individuals that are heterozygous for the gene (AS)have enhanced resistance to malaria over normal individuals (AA).Individuals with severe sickle-cell anemia (SS)usually die before reproduction.If this population moves to an area without malaria,what will happen to the allele frequency of the A allele over time?

Accepted Answer

In the absence of malaria, the selective advantage for carrying the S allele (resistance to malaria) disappears. Individuals with AA genotype do not face the increased risk of malaria and thus are not at a selective disadvantage. Over time, the frequency of the A allele will increase because the selective pressure that favored the AS genotype (malaria resistance) is no longer present.

Question 18

If the frequency of an autosomal recessive trait in humans is 1 out of 100 births,what would be the expected frequency of heterozygote carriers for the trait if we assume that the gene is in Hardy-Weinberg equilibrium?

Accepted Answer

In Hardy-Weinberg equilibrium, the frequency of homozygous recessive individuals (affected by the trait) is q^2, where q is the frequency of the recessive allele. We know that q^2 = 1/100, so q = 0.1. The frequency of heterozygous carriers is 2pq, where p is the frequency of the dominant allele. Since we're assuming the gene is in equilibrium, p = 1 - q = 0.9. Thus, the frequency of carriers is 2 x 0.1 x 0.9 = 0.18 or 18%. Therefore, the correct answer is C.

Question 19

The several hundred species of picture-winged fruit flies of the Hawaiian Islands are genetically very similar,yet they all differ markedly from their ancestral population in Asia.This is probably an example of ________

Accepted Answer

The fact that the Hawaiian picture-winged fruit flies differ from their ancestral population in Asia suggests that a small subset of the original population colonized the Hawaiian Islands and their genetic makeup has diverged from the original population due to random genetic drift. This is an example of the founder effect.

Question 20

A population of flowers is in Hardy-Weinberg equilibrium with an allele frequency for white flowers (w)of 40%.What percentage of the flowers will have the colored or dominant phenotype?

Accepted Answer

In Hardy-Weinberg equilibrium, the frequency of the dominant phenotype can be calculated using the formula: p^2 + 2pq, where p is the frequency of the dominant allele and q is the frequency of the recessive allele. Given q (frequency of w, the recessive allele) is 40% or 0.4, p (frequency of the dominant allele) is 60% or 0.6. Thus, the frequency of the dominant phenotype = (0.6)^2 + 2(0.6)(0.4) = 0.36 + 0.48 = 0.84 or 84%.

Quiz 20: Genes Within Populations