ch 23
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?
All of the alleles of all the genes that were passed from the 60 parents to the 48 new cubs
In nature, large populations are often composed of several smaller groups called populations.
Blank 1: local
How is the allele frequency of a population calculated?
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.
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?
0.6
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
The ______ of a population consists of all of the alleles of every gene in all of the individuals of that population. Multiple choice question.
gene pool
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?
A - 0.48; a - 0.52
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?
About 1%
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)?
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 divided by the total number of all the alleles for the same gene in the population.
How can we calculate the frequency of a specific genotype in a population?
The number of individuals with this genotype in the population is divided by the total number of individuals in the population.
How can we calculate the frequency of a specific genotype in a population? Multiple choice question.
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: 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.
dd, wdd= 1.0
If a high chi-square value is obtained when comparing observed and expected genotypes in a population, we can state that the population is in .
disequilibrium
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
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
evolutionary change is not occurring in this population.
Which of the following is an accurate depiction of the Hardy-Weinberg equation for a gene with two alleles?
p2 + 2pq + q2 = 1
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
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
the allele frequency of the p allele.
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
the genotype frequency of the DD genotype.
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
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?
0.8
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?
A and B only
Which of the following correctly defines a population of sexually reproducing species for the purposes of population genetics?
A group of individuals that occupy the same area and can interbreed with each other
Which of the following is a situation in which directional selection may be observed?
A new allele, which promotes higher fitness in organisms that carry it, is introduced in a population (for example, by a random mutation).
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.
Animals in the population mate randomly, regardless of their genotype for the Col gene No new mutations in the Col gene No natural 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?
G - 0.20; g - 0.80
In order to derive the Hardy-Weinberg equation, the two scientists assumed that Multiple choice question.
gametes are independently chosen at random from the population's gene pool.
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.
polymorphisms.
The field of genetics studies the extent of genetic variation within groups of people over time.
population
Microevolution is best described as
the change in a population's gene pool from generation to generation.
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.
Blank 1: polymorphism, polymorphic, or 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.
Blank 1: population
The ______ of a population is the sum of the frequencies of all genotypes, each one multiplied by its respective relative fitness.
mean fitness
Which field of genetics would study the extent of genetic variation within groups of people over time?
Population genetics