Genetic - Chap 27
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
Consider a population in which a gene is present in the form of two alleles with the following frequencies: A=0.4, and a=0.6. The value of f (how much genotype frequencies deviate from Hardy-Weinberg equilibrium due to non-random mating) for this population is 0.3. What would the predicted frequency of heterozygotes be in this population?
0.34 Using the formula 2pq(1-f). Thus, 2(0.4)(0.6)(1-0.3) = 0.34
Which of the following is a typical mutation rate (with proper units) for a gene in a natural population?
10^(-6) per gene per generation
Consider an individual that has an inbreeding coefficient of 4%. What is the probability that this individual is homozygous dominant for the the cystic fibrosis gene because he inherited the same allele twice from a common ancestor (due to inbreeding)?
2% A 4% inbreeding coefficient means that there is 4% chance that a gene is homozygous (could be dominant or recessive) due to inheritance from the same ancestor. Since each gene in eukaryotes is represented by two alleles, the probability that the individual is homozygous dominant is only 2%. Likewise, the probability that the individual is homozygous recessive, is also 2%.
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
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.
The relative (compared to other genotypes) likelihood that a genotype will contribute its alleles to the next generation is known as __________ _________
Darwinian fitness
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
How is a protein domain related to the exons of a gene?
Each protein domain tends to be encoded by a single exon, or in some cases a few, adjacent exons.
______ occurs when two genetically related individuals (for example, cousins) mate.
Inbreeding
The letter f is used in population genetics to denote how much genotype frequencies deviate from Hardy-Weinberg equilibrium due to non-random mating. If a population has a value of f = -0.5, what type of non-random mating process is occurring and what is its effect on heterozygote frequencies?
Outbreeding; heterozygote frequencies will be higher than predicted by Hardy-Weinberg
You are observing two populations of the same animal species. Population 1 consists of 46 individuals, while population 2 consists of 3325 individuals. Which population is more susceptible to genetic drift?
Population 1 is more susceptible.
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.
Which of the following best defines the inbreeding coefficient?
The probability that two identical alleles in an individual are inherited by descent from the same common ancestor.
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
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 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.
Consider a population and a gene that has two alleles in this population, designated as E and e. If you divide the number of all the copies of the e allele in the population by the total number of copies of both alleles (E and e) in the population, you will calculate the ______.
allele frequency of the e allele
For random mating to occur, individuals must choose their mates irrespective of their genotype/phenotype. When this condition is violated, non-random mating is occurring, also known as ______ mating.
assortative
For random mating to occur, individuals must choose their mates irrespective of their genotype/phenotype. When this condition is violated, non-random mating is occurring, also known as _______ mating.
assortative
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
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
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 term genetic _______ refers to any random change in the frequencies of alleles in a population.
drift
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
By looking at many different proteins and the genes that encode them in a variety of eukaryotic organisms, scientists have determined that a protein domain tends to be encoded by one or a few (usually adjacent)
exons
Population genetics is concerned with the ______.
extent of genetic variation within a group of individuals
In DNA ________ , an individual is characterized based on the repetitive sequences in his or her genome.
fingerprinting or profiling
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 these situations, an equilibrium is reached, in which both alleles of the gene are maintained in the population.
heterozygote advantage
During _______ gene transfer, genetic material from a donor organism is incorporated into a recipient organism which is not the donor's offspring.
horizontal
The transfer of genetic material from one species to another (regardless of the exact mechanism) is called ______.
horizontal gene transfer
Sometimes, both alleles of a gene in a particular individual are identical because they were actually inherited by descent from the same common ancestor. The probability of that occurring is called the _______ coefficient.
inbreeding
The change in a population's gene pool from one generation to the next is known as ______.
microevolution
A _________ is any change in the DNA of an organism, for example, a change in DNA sequence or the structure and number of chromosomes.
mutation
According to the theory of _______ ________ , individuals with alleles leading to greater reproductive success will be more likely to produce offspring and pass those alleles to the next generation.
natural selection
Most eukaryotic species contain short sequences, typically a few base pairs to a few thousand base pairs long, that are repeated many times throughout the genome. Using a general term, these are called ______ sequences.
repetitive
Mutations occur when the DNA of an organism changes. Changes often happen in gene ______ , but may also involve the structure and number of chromosomes.
sequences
Microevolution is best described as ______.
the change in a population's gene pool from generation to generation
Inbreeding and outbreeding can cause certain features of populations to deviate from Hardy-Weinberg equilibrium. From the list below, choose the statements that describe commonalities between inbreeding and outbreeding. Assume that no other evolutionary processes are acting on the genes in question.
- Both inbreeding and outbreeding alter the relative proportions of heterozygotes in a population. - Neither inbreeding or outbreeding affect the allele frequencies in a population.
Which 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.
In certain populations, natural selection can favor the maintenance of 2 or more alleles in a population. An example of this is ______ selection.
balancing
The probability that a gene will be altered as a result of mutation is known as the mutation
rate
When the hypothesis that the allele and genotype frequencies are in Hardy-Weinberg equilibrium is rejected, it can be stated that the population is in ________ .
disequilibrium
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?
- 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).
Choose the two most important results of the founder effect on the newly founded population.
- The founding population typically has very different allele frequencies from those of the original population. - The founding population typically has less genetic diversity than the original population.
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?
Directional selection
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
Genetic drift is the _____ in a population.
random change in allele frequencies
If an individual has an inbreeding coefficient of 7%, it means that ______.
the probability that a gene in this individual is homozygous due to inheritance from a common ancestor is 7%
In ________ selection, individuals at one extreme of a phenotypic distribution are more likely to survive and reproduce in a particular environment.
directional
The genetics field that is concerned with the extent of genetic variation within a group of individuals and changes in that variation over time is _______ genetics.
population
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).
When individuals migrate, alleles can be transfered from one population to another population. This commonly referred to as
Gene Flow
Natural selection is the phenomenon in which certain phenotypes have ______ than other phenotypes.
greater reproductive success
Which of the following is an accurate depiction of the Hardy-Weinberg equation for a gene with two alleles?
p^(2) + 2pq + q^(2) = 1
In disruptive selection, ______.
two or more alleles are maintained in a heterogeneous environment
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
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
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.
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
A population would be described as being in ______ if a high chi-square value is obtained when testing whether the allele and genotype frequencies are in Hardy-Weinberg equilibrium.
disequilibrium
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
The ________ _________ of a population consists of all of the alleles of every gene in all of the individuals of that population.
gene ; pool
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.
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
In order to derive the Hardy-Weinberg equation, the two scientists assumed that ______ population's gene pool..
gametes are independently chosen at random from the
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
