genetics ch.23

In a population of frogs, a gene is found in two forms - D, and d. The numbers of individuals with different genotypes for that gene are 30 (DD), 18 (Dd), and 12 (dd). What is the frequency of the heterozygous genotype? Multiple choice question. 0.30 0.65 (Genotype frequency = # individuals with a particular genotype/Total # in population. Thus, 18/60 = 0.3.) 0.18 0.43

0.30

You are studying a population of birds that has recently become established on an island some 1,000 km from the mainland. On the mainland, these birds mostly consume fleshy fruits, however, on the island they are forced to eat nuts that have to be cracked open with a strong beak. What type of selection is most likely to occur for genes that determine the size and strength of the beak in these birds? Multiple choice question. Directional selection Disruptive selection Stabilizing selection

Directional selection

A gene is present in a population in two forms. The frequency of allele G is 0.3, while the frequency of allele g is 0.7. The most fit genotype is gg, with a relative fitness of 1. The relative fitness of the heterozygotes is 0.6, and that of the dominant homozygotes is 0.3. In this case of directional selection (which favors the g allele), what would the frequencies of the two alleles (G and g) be after one generation? Multiple choice question. G - 0.25; g - 0.75 G - 0.50; g - 0.50 G - 0.20; g - 0.80 G - 0.40; g - 0.60 (First, you have to calculate the mean fitness of the population. Once you have that, calculate the frequencies of genotypes in the next generation by taking the Hardy-Weinberg predicted formula, multiplying them by the relative fitness and dividing by the mean fitness. For example, for the GG genotype, you would calculate p2wGG/(mean fitness). After you have calculated the expected genotype frequencies, calculate the allele frequencies.)

G - 0.20; g - 0.80

Consider a population of a hypothetical animal, whose fur color is determined by a single gene, called Col. From the list below choose all conditions that must be met in order for this population to be in Hardy-Weinberg equilibrium for the Col gene. Multiple select question. No new mutations in the Col gene No new mutations in any gene (It is only the gene of interest that does not incur any new mutations.) No natural selection Low to moderate levels of genetic drift Animals in the population mate randomly, regardless of their genotype for the Col gene

No new mutations in the Col gene No natural selection Animals in the population mate randomly, regardless of their genotype for the Col gene

Which field of genetics would study the extent of genetic variation within groups of people over time? Multiple choice question. Molecular genetics Behavioral genetics Population genetics Classical genetics

Population genetics

Which of the following are likely reasons for differences in the reproductive success of different genotypes in a population? Multiple select question. Some genotypes are more likely to find mates than others. Some genotypes are more fertile than others. Some genotypes are more likely to continue to live after surviving to reproductive age. Some genotypes are more susceptible to genetic drift than others. Some genotypes are more likely to survive to reproductive age than others.

Some genotypes are more likely to find mates than others. Some genotypes are more fertile than others. Some genotypes are more likely to survive to reproductive age than others.

A population is undergoing directional selection for a gene with two alleles: G, and g. The most fit genotype is GG (relative fitness 1), while the Gg and gg genotypes both have relative fitnesses of 0.5. Which of the following is expected to happen after several generations (assuming that the environment, in which this population lives, is not changing)? Multiple choice question. The mean fitness of the population will decrease. The relative fitness of the GG genotype will increase. (This genotype has the highest fitness.) The relative fitnesses of the Gg and gg phenotypes will decrease. (Relative fitness will not change because the environment is unchanging.) The mean fitness of the population will increase.

The mean fitness of the population will increase.

How is the allele frequency of a population calculated? Multiple choice question. The number of copies of the allele in the population is multiplied by the total number of all the alleles for the same gene in the population. The number of copies of the allele in the population is divided by the total number of all the alleles for all genes in the population. (Allele frequencies for each gene are calculated separately.) The number of copies of the allele in the population is divided by the total number of all the alleles for the same gene in the population. The number of individuals that have this allele in the population is divided by the total number of individuals in the population. (The total number of alleles in the population must be considered. Except for X-linked genes in males, individuals will have two copies of each allele.)

The number of copies of the allele in the population is divided by the total number of all the alleles for the same gene in the population.

Consider a population and a gene present in this population as two alleles: D, and d. For every 100 dd individuals that survive to reproduce, 18 DD and 99 Dd individuals survive to reproduce as well. Which of these three genotypes has the highest Darwinian fitness and what is its value (w)? Assume that all individuals that survive to reproduce have roughly the same number of offspring. Multiple choice question. dd, wdd= 1.0 DD, wDD= 1.0 dd, wdd= 100 DD, wDD= 18 (wDD= 0.18 since 18 DD individuals survive for every 100 dd individuals that survive.) Dd, wDd= 0.98 (wDd= 0.99 since 99 Dd individuals survive for every 100 dd individuals that survive.)

dd, wdd= 1.0

In ____ selection, individuals at one extreme of a phenotypic distribution are more likely to survive and reproduce in a particular environment. Listen to the complete question

directional

Sometimes individuals at one extreme of a phenotypic distribution are favored in a particular environment, for example, selection will strongly favor insects that have very high resistance to an insecticide. In such cases, the type of selection that operates is Multiple choice question. directional selection. diversifying selection. stabilizing selection.

directional selection.

f a high chi-square value is obtained when comparing observed and expected genotypes in a population, we can state that the population is in ____

disequilibirum

The Hardy-Weinberg equilibrium is a mathematical expression, which predicts that, when certain requirements are met, the allele and genotype frequencies of a gene in a population Multiple choice question. do not change over the course of many generations. randomly change over the course of many generations. tend to become equally distributed over the course of many generations (for example, with two alleles, both alleles' frequencies will become 0.5). (Allele and genotype frequencies become constant but not necessarily equally distributed.)

do not change over the course of many generations.

The Hardy -Weinberg equilibrium is used as a null hypothesis, i.e., if a population is in Hardy-Weinberg equilibrium, then Multiple choice question. evolutionary change is occurring in this population. all of the different alleles for a gene in a population have the same frequency. evolutionary change is not occurring in this population.

evolutionary change is not occurring in this population.

In order to derive the Hardy-Weinberg equation, the two scientists assumed that Multiple choice question. gametes are chosen in a specific non-random sequence from the population's gene pool. (The Hardy-Weinberg equilibrium assumes that two gametes are chosen at random from the gene pool.) there is an infinite number of all types of gametes in the population's gene pool. gametes are independently chosen at random from the population's gene pool. there is an equal number of gametes for each allele in the population's gene pool.

gametes are independently chosen at random from the population's gene pool.

Within a large populations, smaller groups who may be separated from other groups by geographic barriers and whose members are likely to interbreed with each other form a ______ population. Multiple choice question. adjacent reproductive local nearby

local

The mechanism of evolution through ___ _____ was proposed by Charles Darwin and Russel Wallace in the 1850s.

natural selection

Which of the following is an accurate depiction of the Hardy-Weinberg equation for a gene with two alleles? Multiple choice question. p2 + q2 = 2pq p2 + 2pq + q2 = 1 p2 + pq + q2 = 1

p2 + 2pq + q2 = 1

The field of ____ genetics studies the extent of genetic variation within groups of people over time. Listen to the complete question

population

Microevolution is best described as Multiple choice question. a random change in the genetic variation of a small population. (Genetic drift refers to random changes in variation.) the change in a population's gene pool from generation to generation. the differential survival of members of a population with a certain genotype. the evolution of a single gene.

the change in a population's gene pool from generation to generation.

In a population of lizards, a gene is found in two forms, B, and b. The number of animals with the three possible genotypes for this gene is as follows: BB - 24; Bb - 42; bb - 9. What is the frequency of the B allele in this population? Multiple choice question. 0.5 0.32 (BB individuals contribute two B alleles while Bb individuals contribute one B allele. Add those contributions together and divide by the total number of alleles.) 0.44 0.6

0.6

A population is undergoing a directional selection for a gene with two alleles, A (with a frequency of 0.4), and a, (with a frequency of 0.6). The relative fitness values for the three genotypes are as follows: wAA=1, wAa=0.5, and waa=0.5. What would be the expected frequencies of the two alleles after one generation? Multiple choice question. A - 0.48; a - 0.52 A - 0.66; a - 0.34 A - 0.50; a - 0.50 A - 0.60; a - 0.40 (First, you have to calculate the mean fitness of the population. Once you have that, calculate the frequencies of genotypes in the next generation by taking the Hardy-Weinberg predicted formula, multiplying them by the relative fitness and dividing by the mean fitness. For example, for the AA genotype, you would calculate p2wAA/(mean fitness). After you have calculated the expected genotype frequencies, calculate the allele frequencies.)

A - 0.48; a - 0.52

Which of the following correctly defines a population of sexually reproducing species for the purposes of population genetics? Multiple choice question. A group of individuals that occupy the same area and compete for the same resources A group of individuals that occupy the same area and can interbreed with each other A group of individuals that live in the same general area and their gene pool

A group of individuals that occupy the same area and can interbreed with each other

You are studying a very rare disease, which affects only 1 in 40,000 individuals. The disease is caused by a recessive allele, such that only individuals with homozygous recessive genotypes are affected. What is the expected frequency of heterozygous carriers in this population? Multiple choice question. About 1% About 2% About 0.005% About 5% (In this problem q2=1/40,000. Use this information to calculate q and p. The frequency of heterozygous carriers is 2pq.)

About 1%

Which of the following is not a reason for differences in the reproductive success of different genotypes in a population? Multiple choice question. Some genotypes can be more likely to find mates. Certain genotypes can be more likely to survive to reproductive age. (Reproductive success depends on the ability to survive and reproduce.) Some genotypes can be more fertile. Certain genotypes are more likely to continue to live after surviving to reproductive age.

Certain genotypes are more likely to continue to live after surviving to reproductive age.

The relative (compared to other genotypes) likelihood that a genotype will contribute its alleles to the next generation is known as ____ ____

darwinian fitness

Suppose a chi-square analysis is performed to test whether the observed genotypes in a population are consistent with the predictions of Hardy-Weinberg equilibrium. Which type of chi-square value will be obtained if a population is in disequilibrium? Multiple choice question. high low moderate

high

In nature, large populations are often composed of several smaller groups called ____ populations.

local

The ______ of a population is the sum of the frequencies of all genotypes, each one multiplied by its respective relative fitness. Multiple choice question. natural selection mean fitness zygote frequency heterozygote advantage

mean fitness

The change in a population's gene pool from one generation to the next is known as Multiple choice question. Hardy-Weinberg's principle. evolutionary drift. natural selection. microevolution.

microevolution.

In population genetics, a gene that exists as two or more alleles in a population is a(n) ______ gene, while one that exists predominantly as a single allele is a(n) ______ gene. Multiple choice question. polymorphic; monomorphic monomorphic; polymorphic (In population genetics, a gene that exists as two or more alleles in a population is a polymorphic gene, while one that exists predominantly as a single allele is a monomorphic gene.)

polymorphic; monomorphic

Most of the traits in a healthy natural population exhibit some level of variation, or ____, that is, they are found in two or more forms.

polymorphism

Consider a population, for which you know the allele composition of three genes. Gene A has three alleles in the following proportions: A1 - 34.4%, A2 - 30%, A3 - 35.6%. Gene B has two alleles in the following proportions: B1 - 67.1%, B2 - 32.9%. Gene C has two alleles in the following proportions: C1 - 99.2%, C2 - 0.8%. Which of those genes is(are) polymorphic? Multiple choice question. A and B only C only A only A, B and C (Gene C is monomorphic.)

A and B only

Which of the following is a situation in which directional selection may be observed? Multiple choice question. Heterozygotes in a population exhibit fitness higher than the fitness of any of the homozygotes. In a population with a continuous phenotypic distribution, two extreme phenotypes are more fit than the intermediate phenotype. (Disruptive selection is operating when both extreme phenotypes have a higher fitness than the intermediate one.) A new allele, which promotes higher fitness in organisms that carry it, is introduced in a population (for example, by a random mutation).

A new allele, which promotes higher fitness in organisms that carry it, is introduced in a population (for example, by a random mutation).

You are studying a rare disease, which affects 1 out of 10000 individuals. The disease is caused by a gene with two alleles: D, and d. Individuals with a dd genotype are affected, while individuals with a Dd phenotype are unaffected carriers. What is the expected frequency of unaffected carriers in the population, assuming this gene is in Hardy-Weinberg equilibrium? Multiple choice question. Approximately 98% (In this problem q2=1/10000. Use this information to calculate q and p. The frequency of heterozygous carriers is 2pq.) Approximately 0.02% Approximately 1%

Approximately 2%

Which of the following (choose all that apply) are conditions that must be met in order for a population to be in Hardy-Weinberg equilibrium for a specific gene of interest? Multiple select question. No new mutations should be appearing in the gene of interest. Immigration and emigration rates must be equal, resulting in no net movement of organisms. The population must be large enough so that no genetic drift is occurring. All of the different genotypes (with respect to the gene of interest) must have equal reproductive success (no selection).

No new mutations should be appearing in the gene of interest. The population must be large enough so that no genetic drift is occurring. All of the different genotypes (with respect to the gene of interest) must have equal reproductive success (no selection).

Which of the following is the best definition of Darwinian fitness as it relates to population genetics? Multiple choice question. The likelihood that a genotype will contribute to the next generation, relative to the dominant homozygous genotype The relative (compared to other genotypes) likelihood that a genotype will contribute alleles to the next generation The frequency of the genotype that is most likely (compared to other genotypes) to contribute alleles to the next generation (It is the likelihood that a genotype will contribute alleles to the next generation, regardless of its frequency.)

The relative (compared to other genotypes) likelihood that a genotype will contribute alleles to the next generation

In a population that is undergoing directional selection, the mean fitness of the population Multiple choice question. decreases with each generation. (Natural selection raises the mean fitness of the population.) increases with each generation. stays constant from generation to generation.

increases with each generation.

Consider a population and a gene that has two alleles in this population, designated as D and d. If you divide the number of individuals with the genotype DD by the total number of individuals in the population, you will calculate Multiple choice question. the genotype frequency of the D allele. (Be sure to distinguish between frequencies of alleles and genotypes.) the genotype frequency of the DD genotype. the allele frequency of the D allele.

the genotype frequency of the DD genotype.

Consider a population and a gene that has two alleles in this population, designated as P and p. If you divide the number of all the copies of the p allele in the population by the total number of copies of both alleles (P and p) in the population, you will calculate Multiple choice question. the genotype frequency of the p allele. (A genotypic frequency is number of individuals with the pp genotype divided by the total number of individuals in the population.) the allele frequency of the p allele. the allele frequency of the P allele. (This calculation would reflect the frequency of the p allele.) the genotype frequency of the pp genotype. (A genotypic frequency is number of individuals with the pp genotype divided by the total number of individuals in the population).

the allele frequency of the p allele.

The ______ of a population consists of all of the alleles of every gene in all of the individuals of that population. Multiple choice question. genotype frequency phenotype frequency gene pool

gene pool

The mean fitness of a population undergoing directional selection is Multiple choice question. always 1 (The value may not be equal to 1 when the population is changing during natural selection.) less than 1 more than 1

less than 1

The mechanism of evolution through ____ ______states that those individuals better adapted to their environment are more likely to survive and reproduce.

natural selection

When scientists study populations, they typically observe high levels of variation in many of the traits that characterize a species. In genetics, variations in traits at the population level are known as Multiple choice question. mutations. alleles. demes. polymorphisms.

polymorphisms.

In genetics, a ____ of a sexually reproducing species consists of a group of individuals of that species, which occupy the same region, and can successfully interbreed with each other. Listen to the complete question

population

Consider a population of cheetahs, inhabiting a protected area in Africa. In 2012, there were 112 cheetahs in this population. During that year, 60 of those animals reproduced and 48 new cubs were born. What constitutes the gene pool of the new generation made of those 48 new cubs? Multiple choice question. All of the alleles of all the genes in the 112 adult animals that made up the population in 2012 All of the alleles of all the genes in the 60 parents that had those 48 cubs (Individuals of one generation constitute a gene pool. Only those parental genes passed to the 48 new cubs will be part of the new gene pool.) All of the alleles of all the genes in the 112 animals in 2012 plus all of the alleles of all the genes in the 48 newborn animals (: Individuals of one generation constitute a gene pool. In turn, individuals that reproduce contribute to the gene pool of the next generation.) All of the alleles of all the genes that were passed from the 60 parents to the 48 new cubs

All of the alleles of all the genes that were passed from the 60 parents to the 48 new cubs

How can we calculate the frequency of a specific genotype in a population? Multiple choice question. The total number of individuals in the population is divided by the number of individuals with this genotype in the population. The number of individuals with this genotype in the population is divided by the total number of individuals in the population. The number of individuals with this genotype in the population is divided by the number of individuals with all other genotypes in the population. (The number of individuals with the genotype must be divided by the number of individuals in the whole population.) The number of individuals with this genotype in the population is divided by the total number of all alleles for this gene in the population. (The number of individuals with the genotype must be divided by the number of individuals in the whole population.)

The number of individuals with this genotype in the population is divided by the total number of individuals in the population.

Consider a population and a gene present in this population as two alleles: F, and f. For every 10 Ff individuals that survive to reproduce, 8 FF and 4 ff individuals survive to reproduce as well. If we assume that all individuals that survive to reproduce have roughly the same number of offspring, what is the relative fitness of the FF genotype in this case? Multiple choice question. 1.0 (This represents the fitness of the Ff individuals, where 10/10 survive to reproduce.) 0.4 (This represents the fitness of the ff individuals, where 4/10 survive to reproduce.) 1.25 0.8

0.8