Chapter 23 + 24 Genetics Smartbook BIO 375
What methodology is used to investigate most polygenic quantitative traits?
Statistical analysis
Heritability is a measurement of the ______.
amount of phenotypic variation due to genetic variation
A large, healthy, natural population typically exhibits a ______ level of SNPs.
high
In _____ assortative mating, individuals tend to choose mates with with similar phenotypes. In _____ assortative mating, individuals tend to choose mates with dissimilar phenotypes.
positive, negative
You are studying two populations of the same species. Population A consists of 100 individuals, while population B consists of 1,000 individuals. Population ______ will have a higher number of new mutations appearing in the next generation, and population ______ will have a higher likelihood of fixation of new mutations.
(1) - population B, (2) - population A
A gene is found in two forms in a population of plants. The two alleles are denoted as B, and b. You determine that the frequency of the B allele in this population is 0.2. If this population was in a Hardy-Weinberg equilibrium, calculate the probability of a heterozygote in the next generation.
0.32
In a population of dairy cows, the phenotypic variance for daily milk production is 5.0 L2. The genetic variance is 2.0 L2, and the environmental variance is 3.0 L2. What is the broad-sense heritability for daily milk production in this group of cattle?
0.40
Arrange the principles of natural selection in the order in which they occur, with the first step at the top.
1. A mutation occurs --- 2. Individuals with --- 3. Over the course ---
Polygenic inheritance is the transmission of a trait that is determined by ______.
2 or more different genes
The average heritability of fingerprint patterns is 0.97. This means that ______.
97% of the phenotypic variance in fingerprint patterns is due to genetic variance
A strong similarity in fingerprint patterns between close relatives was shown by analyzing
?
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
What is a normal distribution?
A frequency distribution that varies in a symmetrical way around an average value
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
What is a discontinuous trait?
A trait that falls into discrete categories
If genetic drift is followed over a great many generations, what is its expected effect on allele frequencies?
Alleles are either lost (frequency of 0%) or fixed (frequency of 100%) in the populations.
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 ______ selection.
Directional
Which of the following are required for gene flow to occur?
Migrants must be fertile and pass their genes to the next generation. Individuals must migrate from one population to another.
Two types of factors can govern microevolution. On one hand, mutation is a constant source of new genetic variation. On the other hand, mechanisms that alter existing genetic variation, such as natural selection and genetic drift, can act to alter existing genetic variation. How do those two types of factors compare in terms of the magnitude of their effect on allele frequencies in a population?
Mutations have a negligible effect on allelic frequencies, while mechanisms such as natural selection and drift can have a dramatic effect.
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.
No natural selection No new mutations in the Col gene Animals in the population mate randomly, regardless of their genotype for the Col gene
Which field of genetics studies the inheritance of complex traits?
Quantitative genetics
Stabilizing selection typically acts on quantitative traits determined by multiple genes. Does stabilizing selection have an effect on the genetic diversity of those genes and if so, what type of effect?
Yes, stabilizing selection tends to decrease the genetic diversity of those genes.
If VA is very large in comparison to VD and VI, then the narrow-sense heritability will be ______ the broad-sense heritability.
approximately the same as
In a natural setting, migration between two populations usually occurs in a bidirectional manner in which some individuals of each population migrate to the other population. As a result of such bidirectional movement, differences in allele frequencies ______.
are reduced
The modification of phenotypes of economically important plants and animals through selective breeding is referred to as
artificial
In _______ selection, natural selection favors the maintenance of two or more alleles in a population. An example of that is the phenomenon of heterozygote advantage. Listen to the complete question
balanced
In certain populations, natural selection can favor the maintenance of two or more alleles in a population. An example of this is ______ selection.
balancing
The length of an ear of corn is an example of a ______ trait.
quantitative
Traits that are ______ often show a continuum of phenotypic variation.
quantitative
The field of genetics that studies the inheritance of complex traits is called
quantitative genetics
Disruptive selection typically acts on ______.
quantitative traits that are influenced by more than one gene.
Genetic drift is the ______ in a population.
random change of allele frequencies
A strong similarity in fingerprint patterns between close relatives was shown by analyzing counts
ridge
A complex trait is a trait that is influenced by ______.
several genes and the environment
Microevolution is best described as ______.
the change in a population's gene pool from generation to generation
True or false: In order to calculate narrow-sense heritability from correlation coefficients, it is necessary to assume that genetics and the environment are independent variables.
true
In bread wheat, the color of the hull can be dark red, white, or various intermediate shades of red. Initial genetic analysis of this trait by Herman Nilsson-Ehle demonstrated that hull color is controlled by ______.
two loci with additive effects
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 every gene that were passed from the 60 parents to the 48 new cubs
In _____ selection, natural selection favors the maintenance of two or more alleles in a population. An example of that is the phenomenon of heterozygote advantage.
Balancing
Which of the following is NOT a reason for differences in the reproductive success of different genotypes in a population?
Certain genotypes are more likely to continue to live after surviving to reproductive age.
A scientist is studying two populations of the same species of birds - one in Michigan, and one in Montana. Both populations are relatively large (with more than 10,000 individuals each). However, the Michigan population has a much lower genetic diversity than the Montana population. Which of the two populations is most likely to have experienced a bottleneck and which of the two populations is currently more susceptible to genetic drift?
The Michigan population likely experienced a bottleneck in the past. Both populations are equally susceptible to genetic drift.
The HbS allele for the human β-globin gene is found in relative high frequencies in certain human populations living in areas where malaria is endemic, despite the fact that individuals homozygous for this allele exhibit sickle cell anemia. What explains this observation?
The heterozygous genotype (HbAHbS) is more resistant to malaria than either of the homozygote genotypes.
Which of the following is the best definition of Darwinian fitness as it relates to population genetics?
The relative (compared to other genotypes) likelihood that a genotype will contribute alleles to the next generation
In _____ selection, individuals at one extreme of a phenotypic distribution are more likely to survive and reproduce in a particular environment.
directional
A trait that can be assigned to a particular phenotypic category is called a(n)
discontinuos
Some traits are quantitative, i.e. they are determined by multiple genes and exhibit a range of phenotypes. For some of those traits, the fitness values for particular genotypes may be higher in one environment and lower in another. When populations with such traits inhabit heterogeneous environments, multiple alleles can be maintained through the action of ______ selection.
disruptive
The ______ of a population consists of all of the alleles of every gene in all of the individuals of that population.
gene pool
When the heterozygotes for a specific gene have higher fitness than either of the corresponding homozygote genotypes (assume a single gene with two alleles), we are observing a situation called
heterozygote advantage
The mechanism of evolution through ____ ____ states that those individuals better adapted to their environment are more likely to survive and reproduce.
natural selection
The mechanism of evolution through was proposed by Charles Darwin and Russel Wallace in the 1850s.
natural selection
A frequency distribution in which a trait varies in a symmetrical way around an average value is called a(n)
normal, bell
A frequency distribution is a graph that shows the ______.
number of individuals in various phenotypic categories
Which of the following is an accurate depiction of the Hardy-Weinberg equation for a gene with two alleles?
p2 + 2pq + q2 = 1
Transmission of a trait determined by two or more different genes is referred to as
polygenic
In population genetics, a gene that exists as two or more alleles in a population is a ______ gene, while one that exists predominantly as a single allele is a ______ 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
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 ______.
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.
population
In disruptive selection,,
two or more alleles are maintained in a heterogeneous environment.
The mean fitness of a population undergoing directional selection is ______.
Less than 1
Mating between close relatives, such as brothers and sisters, is referred to as
inbreeding
The change in a population's gene pool from one generation to the next is known as ______.
microevolution
Consider a single gene with two alleles in a population of wild birds. A situation in which the heterozygotes for that gene have higher fitness than the two homozygote genotypes is known as ____ _____ In this situation, an equilibrium is reached, in which both alleles of the gene are maintained in the population.
Heterozygote advantage
Which of the following best explains the high prevalence of the HbS allele of the human β-globin gene in populations living in areas of high malaria prevalence?
This gene is under balancing selection due to heterozygote advantage in those areas.
A population that has experienced a bottleneck is highly susceptible to genetic drift ______.
during the initial bottleneck and during the generations following the bottleneck when the population size is small.
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
True or false: Quantitative traits are usually discontinuous.
false
Sometimes populations become susceptible to genetic drift via the ______ effect. This happens when a small group of individuals separates from a larger population and migrates to a different site, where it establishes a colony.
founder
The relative (compared to other genotypes) likelihood that a genotype will contribute its alleles to the next generation is known as
Darwinian fitness
The human population known as the Old Order Amish of Lancaster County exhibits an unusually high frequency of the genetic disease Ellis-van Creveld syndrome. What explains that observation?
This population was founded by a very small group of people.
A group of individuals from a larger population can migrate to a new area and establish a colony, which will be highly susceptible to genetic drift. This is known as the ______ effect.
Founder
You are studying two populations of an animal species. Population A is made of 300 individuals, while population B is made of 56,000 individuals. You are interested in following a new mutation until it gets fixed by genetic drift. In which of the two populations will it take fewer generations for a new allele to be fixed?
Population A
What is the most common type of polymorphism found in natural populations, including human populations?
SNPs
Which of the following are likely reasons for differences in the reproductive success of different genotypes in a population?
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.
selection acts on quantitative traits determined by multiple genes. In this type of selection, individuals with intermediate phenotypes have higher fitness and are selected for, while extreme phenotypes are selected against.
Stabilizing
According to the principles of natural selection, a mutant allele will increase in the population if it is ______ to reproduction and survival.
beneficial
A healthy population can become highly susceptible to genetic drift if its size is dramatically reduced due to natural phenomena, such as earthquakes or droughts. This is known as the ______ effect.
bottleneck
The ____ effect is observed when a population's size is dramatically reduced due to natural events, such as earthquakes and flood, or due to human destruction of habitat.
bottleneck
Characteristics that are determined by several genes and are also influenced by environmental factors are called
complex
A quantitative trait that does not fall into discrete categories is referred to as a(n) trait
continuous
Which type of selection is also known as diversifying selection because it tends to favor the survival of two or more different phenotypes in a heterogeneous environment?
disruptive selection
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 ______ over the course of many generations.
do not change
A continuous trait is a quantitative trait that ______.
does not fall into discrete categories
The term genetic ____ refers to any random change in the frequencies of alleles in a population.
drift
In order to derive the Hardy-Weinberg equation, the two scientists assumed that
gametes are independently chosen at random from the population's gene pool.
In nature, large populations are often composed of several smaller groups called ______ populations
local
Which of the following are examples of quantitative traits?
Number of bristles in Drosophila Speed of flight in birds Blood pressure in humans
Which field of genetics would study the extent of genetic variation within groups of people over time?
Population genetics
What is the effect of population size (N) (if any) on the probability of fixation of a new allele due to genetic drift?
The higher N is, the lower the chance that a new mutation will become fixed.
Is the size of a population related to the average number of generations needed to achieve fixation of a newly appeared mutation, and how?
The larger the population, the more generations will be required, on average, to achieve fixation of a new allele.
The weight of a human baby at birth is a quantitative trait determined by the activity of many genes. Babies with very low or very high birth weights have a decreased chance of survival, while babies with intermediate birth weights have much better chances of survival. What can you hypothesize about the genetic diversity of genes that determine birth weight in humans?
They are under stabilizing selection, which should decrease their genetic diversity.
A founding population usually has lower genetic diversity than the original population it came from. For those alleles that are shared by the two populations, how are allele frequencies different (or similar)?
Usually, the allele frequencies in the founding population are very different from those of the original population.
If a population is in Hardy-Weinberg equilibrium for a gene with two alleles (G and g), and the frequency of the g allele is very low, we can predict that most of the organisms in this population will have the ______ genotype.
GG
Over time, genetic drift can lead to the fixation of an allele. What types of alleles are usually fixed by drift?
Genetic drift is random, so deleterious, beneficial, or neutral alleles can become fixed.
The field of __ genetics studies the extent of genetic variation within groups of people over time.
population
Which type of selection tends to select against extreme phenotypes for a quantitative trait, because individuals with intermediate phenotypes have the highest relative fitness values?
Stabilizing selection
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?
The population must be large enough so that no genetic drift is occurring. No new mutations should be appearing in the gene of interest. All of the different genotypes (with respect to the gene of interest) must have equal reproductive success (no selection).
Within 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(n) ______ population.
local
The ______ of a population is the sum of the frequencies of all genotypes, each one multiplied by its respective relative fitness.
mean fitness
Which of the following phenomena is responsible for introducing new genetic variation in a population?
mutation
