chapter 19 bio 101

For a gene with two alleles whose frequencies are p and q, the Hardy-Weinberg equation states that the genotypes that are possible for the population are p2 + 2pq + q2, which is equal to

(p + q)2.

Consider a population with 100 cats. If 72 cats are black and 28 cats are white, what is the phenotypic frequency of black cats?

.72

If the frequency of allele A is 0.6 and the frequency of allele a is 0.4, what is the probability that an individual will receive two a alleles?

0.16

In a population of tree frogs, the observed frequencies of the GG, Gg, and gg genotypes for a certain trait are 0.1, 0.6, and 0.3, respectively. If this population was in Hardy-Weinberg equilibrium, what would be the expected frequency of GG? Hints: (1) Consider this population and calculate the frequency of the G allele first, then calculate the expected frequency of GG. (2) The observed and expected frequencies of a genotype are not necessarily the same number.

0.16

Regarding a particular trait in a population of painted turtles (Chrysemys picta), 14% of the turtles have the homozygous dominant genotype, 70% are heterozygous, and 16% are homozygous recessive. What is the value of q2?

0.16

In a population of painted turtles, a dominant allele for a certain trait occurs at a frequency of 0.1. If this population is in Hardy-Weinberg equilibrium, what would be the expected frequency of heterozygotes? Assume there are only two alleles for that trait.

0.18

If the frequency of heterozygotes in a population of mice is 0.48 for a particular gene, what would be the frequency of heterozygotes in future generations if the population is in Hardy-Weinberg equilibrium?

0.48

Consider a gene in a population of fruit bats. There are two alleles for this gene, A and a, that occur in a population with the frequencies 0.8 and 0.2, respectively. If the population is in Hardy-Weinberg equilibrium, what genotype frequencies will be observed?

0.64 AA, 0.32 Aa, and 0.04 aa

Consider a population with 100 cats. If 72 cats are black and 28 are white, what is the phenotypic frequency of black cats?

0.72

You are examining allele frequencies of a gene in a population of frogs. This gene has two alleles, T and t. If the frequency of the dominant allele (T) is 0.25, then the frequency of the recessive allele (t) is

0.75

In a population with three possible genotypes for a particular gene, what is the sum of all the genotype frequencies equal to?

1

The allele frequency is calculated by dividing the number of copies of a given _______________ in a population by the total number of ___________ in that population.

1. allele 2. alleles

If the probability of an individual being Bb is pq and the probability of an individual being bB is qp, what is the total probability that an individual will be heterozygous in this population?

2pq

In the frequency of allele B is p and the frequency of the alternative allele b is q, then what is the probability that an individual be heterozygous (Bb)?

2pq

Select all of the following that increase the chances of genetic drift in a population.

A few individuals of a population become isolated. Only a few individuals contribute gametes to the next generation. A population becomes very small.

Select all of the following events that could lead to a population bottleneck.

A natural disaster such as an earthquake or flood Human destruction of habitat An infectious disease that kills a large proportion of the population

Select all of the following that could cause evolutionary change by natural selection.

A plant with an enzyme that makes it disease-resistant A moth that has a gene for cryptic (camouflage) coloration

In what type of selection does a breeder select for desirable characteristics in organisms?

Artificial selection

___________ mating is a type of nonrandom mating in which phenotypically similar individuals mate.

Assortative

Which evolutionary mechanism changes genotype frequencies but does not change allele frequencies?

Assortative mating

Why does selection occur?

Because some individuals in a population possess more favorable phenotypes than others.

In a large population that is not subject to mutation, migration, selection, or nonrandom mating, the proportions of genotypes are stable and the population is said to be in_____________. equilibrium, named after the scientists who described this principle.

Blank 1: Hardy Blank 2: Weinberg

Because of_________ , ________ even a harmful allele that is selectively disadvantageous can increase in frequency in a small population.

Blank 1: genetic Blank 2: drift

Mummichog fish have variable allele frequencies for the gene that produces the enzyme

Blank 1: lactate Blank 2: temperatures or locations

This figure illustrates that the difference between the color of an animal and the background color of the environment which it inhabits can determine the probability of capture by a predator. This phenomenon is known as background

Blank 1: matching

What theory was widely accepted in the mid-1800s and predicted that new genetic variants in populations would eventually disappear in subsequent generations?

Blending inheritance

Which of the following accurately describes variations in enzyme alleles related to geographical location?

Certain enzyme allele frequencies are more common in northern populations and become progressively less common at more southern locations.

____________ mating is a type of nonrandom mating where phenotypically different individuals mate more often.

Disassortative

Natural selection can lead to_________ if variation is genetically based.

Evolution

Select all of the following that are examples of the founder effect.

Evolution of organisms on distant oceanic islands The start of a new population from the seed of a plant that has been carried to a distant location Increased frequency of a genetic feature in a population established by a small number of individuals

For natural selection to occur, variation in traits must be which of the following?

For natural selection to occur, variation in traits must be which of the following?

What evolutionary process is occurring when individuals belonging to adjacent populations mate with each other?

Gene flow

Which of the following agents of evolutionary change occurs when alleles move from one population to another?

Gene flow

Evolutionary change is not caused by phenotypic variation if the phenotypic variation lacks which of the following?

Genetic basis

What evolutionary mechanism results in random changes in allele frequencies from one generation to the next?

Genetic drift

Many 19th century scientists believed that natural selection always favored an optimal form, and therefore would tend to reduce or eliminate which of the following?

Genetic variation

What did the scientists Godfrey Hardy and Wilhelm Weinberg explain?

Genetic variation in a population.

What changes in genetic variation in a population are expected after a population bottleneck followed by population growth and a return to the original population size?

Genetic variation will be decreased.

Select the statement that describes nonrandom mating.

Genetically similar individuals preferentially mate with each other.

After Mendel's work was rediscovered, what scientists explained why a population doesn't always come to be composed solely of individuals with the dominant phenotype?

Hardy and Weinberg

Select all of the following that could cause a population to deviate from Hardy-Weinberg equilibrium.

Immigration of homozygotes Emigration from the population Reduction to a small population size Natural selection favoring heterozygotes

How does genetic drift affect allele frequencies?

It changes allele frequencies randomly

What effect does background matching have on the probability of capture by a predator?

It decreases it

Consider population 1 in which the frequency of allele A = 0.1 and population 2 in which the frequency of allele A = 0.7. What will happen to the frequency of A in population 1 if individuals from population 2 move into population 1?

It will increase.

Consider a gene with two alleles, one dominant, and the other recessive. If this population is in Hardy-Weinberg equilibrium with respect to this gene, what would happen to the dominant allele from generation to generation?

Its frequency will remain unchanged.

If blending inheritance occurred in Mendel's pea plants (Pisum sativum), a purple-flowered plant crossed with a white-flowered plant would produce plants with which color flowers?

Light purple

Select all of the following processes that can cause changes in allele or genotype frequencies in populations.

Natural selection Mutations Nonrandom Mating Genetic drift Gene flow

Self-fertilization in plants is an example of what evolutionary process?

Nonrandom mating

What evolutionary process is occurring if individuals with certain genotypes mate with each other more commonly than would be expected on a random basis?

Nonrandom mating

What conclusion can be drawn from the observation that a population is not in Hardy-Weinberg equilibrium?

Nonrandom mating was occurring.

What hypothesis would you investigate if you observed a population that had a higher frequency of homozygotes than that predicted by the Hardy-Weinberg equation?

Nonrandom mating was occurring.

What can be affected by dominance and recessiveness of alleles in a population that is in Hardy-Weinberg equilibrium?

Phenotypic frequencies

If population 1 is in Hardy-Weinberg equilibrium such that p = 0.7 and q = 0.3, select all of the following that would result if mating began to occur with the adjacent population 2 in which p = 0.1 and q = 0.9.

Population 1 will shift out of Hardy-Weinberg equilibrium. In population 1, q will increase. In population 2, p will increase.

Select reasons why genetic variation within natural populations was a puzzle to Darwin and other scientists in the 19th century.

Scientists thought that selection should always favor an optimal form. Genetic variants were expected to be diluted to the point of disappearing in future generations. Segregation of alleles among progeny of hybrids was not understood.

Select all of the following that are examples of gene flow.

Seeds being blown by the wind far from their origin. Migration of animals from one place to another. The carrying of pollen by insects over great distances. Drifting of the gametes of marine animals

What could cause the frequency of an allele to increase between generations?

Selection favoring the allele

Select all of the following that are examples of nonrandom mating.

Selection of mates with similar phenotypes Selection of mates with dissimilar phenotypes

The low level of genetic diversity among northern elephant seals is best explained by which of the following?

The bottleneck effect

The prevalence of disorders such as polydactylism among some Amish populations in the United States is best explained by which of the following?

The founder effect

Select the reasons why a population bottleneck can lead to genetic drift, as illustrated in the image.

The gene pool of the surviving members of the population may be different from the original gene pool. Very few individuals contribute to the next generation. Small populations are more sensitive to genetic drift.

Select all of the following that can result from a population bottleneck.

The genetic diversity of the surviving population is usually lower than the genetic diversity of the original population. The surviving members of the population may have different allele frequencies than the original population.

Random changes in allele frequencies in small populations are known as

The larger the population, the lower the chance of genetic drift is

Which of the following examples illustrates the bottleneck effect?

The low level of genetic diversity among northern elephant seals

What is gene flow?

The movement of alleles into or out of a population.

Select the conditions that must be met for a population to be in Hardy-Weinberg equilibrium.

The population is very large. No new mutations occur. Mating is random.

Select all of the following that can result from assortative mating.

The proportion of heterozygotes in the population decreases. The proportion of homozygotes in the population increases.

The phenotype frequency is calculated by dividing the total number of individuals with a particular phenotype by which of the following?

The total number of individuals in that population

Select all of the following criteria that must be present for natural selection to occur and cause evolutionary change in a population.

Variation must have a genetic basis Variation must result in differences in the number of offspring surviving in the next generation Variation must exist among individuals

The number of copies of an allele in a population divided by the total number of all alleles for that gene in a population is the

allele frequency

Dominance and recessiveness of alleles can affect how ______, but will not affect how ______.

an allele is expressed; how allele frequencies change through time

The bottleneck effect occurs when allele frequencies change due to

an event that drastically reduces population size.

Natural selection favors characteristics that confer a survival advantage because these traits

are also likely to increase the likelihood of reproduction.

In artificial selection, the ______ selects individuals with desired characteristics to produce offspring, and in natural selection, the ______ selects which individuals will produce the most offspring.

breeder; environment

We know that selection can occur based on climatic conditions, because biologists have found that

enzyme allele frequencies can vary with geographic latitude.

if a population is not in hardy- weinberg equilibrium then ______ processes are operating

evolution

True or false: Mutation and gene flow are equally important in determining how allele frequencies change.

false

The Hardy-Weinberg equation assumes that

gametes combine randomly.

In disassortative mating,

individuals with dissimilar phenotypes are more likely to mate.

In assortative mating,

individuals with similar phenotypes are more likely to mate.

According to the theory of blending Inheritance, offspring were expected to be phenotypically______________ relative to their parents, which would dilute any new genetic variants.

intermediate

A characteristic that confers a survival advantage

is likely to also increase reproductive success and, as a consequence, favored by natural selection.

Hardy-Weinberg equilibrium requires that the population size is __________ and that mating is __________.

large, random

What is the ultimate source of all new alleles?

mutation

is the ultimate source of genetic variation.

mutation

A population bottleneck could be caused by

natural disaster

Mutation can affect allele frequencies because it causes

one allele to change to another.

In a population that is in Hardy-Weinberg equilibrium, proportions of genotypes are

p and q

For a gene with two alleles, B and b whose frequencies are p and q respectively, the probability that an individual receives a B allele from its mother and a B allele from its father is which of the following?

p2

Which is a correct version of the Hardy-Weinberg equation for genotype frequencies in a population in equilibrium?

p2 + 2pq + q2 = 1

Selection occurs because some individuals in a population have more favorable ______ than others in the same population and leave more progency than others

phenotypes

If a gene has two alleles R and r, the frequency of the R allele can be designated as p, and the frequency of the r allele can be designated as

q

Select all of the following that add to a frequency of 1 (or 100%) for a particular gene in a population.

sum of genotype frequencies sum of allele frequencies

A dramatic reduction in population size due to a natural disaster or destruction of habitat and the resulting change in the allele frequencies of the new population is called

the bottleneck effect.

The change in allele frequencies that occur due to the colonization of a new location by a small group of individuals is called

the founder effect.

New mutations are not a major factor affecting the allele frequencies in a population because

the rate at which new mutations occur is low.

For a population to be in Hardy-Weinberg equilibrium,

there must be no migration into or out of the population.

The caterpillar of the butterfly Colias eurytheme can be a pale green color or a bright yellow color. The yellow caterpillars are usually found in very low frequency because ____.

they are not camouflaged as well as the green ones

True or false: Genetic drift could cause an allele that increases fitness to be lost from a population.

true

True or false: Genetic drift, mutations, and nonrandom mating are three agents that can act to produce evolutionary changes in a population.

true

True or false: The Hardy-Weinberg equation assumes that gametes combine with one another randomly with respect to their genotypes.

true