Chp. 27 Population Genetics
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
Consider a population of cheetahs, inhabiting a protected area in Africa. In 2012, there were 112 cheetah 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
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
Choose the two most important results of the founder effect on the newly founded population.
The founding population typically has less genetic diversity than the original population. The founding population typically has very different allele frequencies from those of the original population.
Founder Effect
a change in allele frequencies that occurs when a small group of individuals separates from a larger population and establishes a colony in a new location
Single-nucleotide polymorphism (SNP)
a genetic polymorphism within a population in which two alleles of the gene differ by a single nucleotide
Microsatellite
a molecular marker composed of many repeated copies of a short sequence
negative frequency dependent selection
a pattern of natural selection in which the fitness of a genotype decreases when its frequency become higher
Balancing Selection
a pattern of natural selection that favors the maintenance of two or more alleles in a population; it may be due to heterozygote advantage or negative frequency-dependent selection
Conglomerate
a population composed of members of an original population plus new members that have migrated from another population
Minisatellite
a repetitive sequence that was formerly used in DNA fingerprinting
Local Population
a segment of a population that is somewhat isolated. These members are more likely to breed with one another.
When a population's size is dramatically reduced due to natural events, such as earthquakes and flood, or due to human destruction of habitat, the phenomenon is termed the _________ effect.
bottleneck
Microevolution
changes in a populations gene pool with regard to particular alleles over measurable periods of time
Genetic Drift
changes in allele frequencies in a population due to random flunctuations
Individuals at one extreme of a phenotypic distribution are more likely to survive and reproduce in a particular environment in ___________ selection.
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 ____________ 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
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
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
Any random change in the frequencies of alleles in a population is called genetic ________
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 change in a population's gene pool from one generation to the next is known as ___________
evolutionary drift
Outbreeding
sexual reproduction between genetically unrelated individuals
Inbreeding
sexual reproduction between two genetically related individuals
Assortive Mating
sexual reproduction in which individuals preferentially breed with each other based on their phenotypes
Repetitive Sequences
short sequences that occur many times within a species genome
Mean Fitness of the Population
the average fitness of a population, calculated by considering the frequencies and fitness values for all genotypes
Microevolution is best described as ___________
the change in a population's gene pool from generation to generation
Population Genetics
the field of genetics that is primarily concerned with the extent of genetic variation within a group of individuals and changes in that variation over time
Mutation Rate
the likelihood that a gene will be altered by a new mutation
Exon Shuffling
the phenomenon in which an exon and its flanking intron from one gene are inserted into another gene
Which of the following is an accurate depiction of the Hardy-Wienberg equation for a gene with two alleles?
P^2+2pq+q^2=1
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
Gene Pool
all of the alleles of every gene within a particular population
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.
assortive
The Hardy-Weinberg equilibrium is used as a null hypothesis, ie. if a population is in Hardy-Weinberg equilibrium, then ________
evolutionary change is not occurring in this population
Polymorphism
the prevalence of two or more phenotypic forms in a population
Horizontal Gene Transfer
the transfer of genes from one individual to another individual that is not its offspring
Population
a group of individuals of the same species that occupy the same region and can interbreed with one another
In certain populations, natural selection can favor the maintenance of two or more alleles in a population. An example of this is __________ selection.
balancing
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
By looking at many different proteins and 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
The _________ ______ of a population consists of all of the alleles of every gene in all of the individuals of that population.
gene pool
Natural selection is the phenomenon in which certain phenotypes have _________ than other phenotypes
greater reproductive success
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
When the heterozygotes for a specific gene have higher fitness than either of the corresponding homozygous genotypes (assume a single gene with two alleles), we are observing a situation called _____________
heterozygote advantage
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
Directional Selection
natural selection that favors an extreme phenotype. This usually leads to the fixation of the favored allele.
Stabilizing Selection
natural selection that favors individuals with an intermediate phenotype
Disruptive Selection
natural selection that favors the maintenance of two or more alleles in heterogenous environments, resulting in two or more phenotypes
Genotype Frequency
number of individuals with a particular genotype in a population/total number of individuals in a population
Hardy-Weinberg equation
p^2 + 2pq + q^2 = 1
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
Natural Selection
refers to the process whereby differential fitness acts on the gene pool. When a mutation creates a new allele that is beneficial, the allele may become prevalent within future generations because the individuals possessing the allele are more likely to reproduce and pass it to their offspring
Genetic material from a donor organism is incorporated into a recipient organism in which is not the donor's offspring during _________ gene transfer
horizontal
The transfer of genetic material from one species to another (regardless of the exact mechanism) is called ________
horizontal gene transfer
Disequilibrium
in population genetics, refers to the condition of a population that is not in the Hardy-Weinberg equilibrium
Reproduction between two identically related individuals, such as cousins, is called __________
inbreeding
Any change in the DNA of an organism, for example, a change in DNA sequence or the structure and number of chromosomes is called a(n) __________
mutation
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
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
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%
Inbreeding Coefficient (F)
the probability that two alleles for a given gene in a particular individual will be identical because both copies are due to descent from a common ancestor
Darwinian Fitness
the relative likelihood that a genotype will contribute to the gene pool of the next generation as compared with other genotypes
Relative Fitness
the reproductive succes of a genotype relative to the maximum reproductive success of other genotypes in the population
Gene Flow
transfer of alleles or genes from one population (a donor population) to another, thereby changing the recipient populations gene pool
In disruptive selection, _____________
two or more alleles are maintained in a heterogeneous environment
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
When individuals migrate, alleles can be transferred from one population to another population. This is commonly referred to as __________ _______.
Gene Flow
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 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 likelihood that a genotype will contribute alleles to the next generation (compared to other genotypes)
Selection Coefficient (S)
a measure of the degree to which a genotype is selected against, equal to one minus the fitness value, s=1-w
Bottleneck Effect
a mechanism that can give rise to genetic drift; occurs when most members of a population are eliminated without any regard to their genetic composition
DNA fingerprinting
a technology for identifying a particular individual based on properties of his or her DNA
Monomorphic
a term used to describe a trait that is found in only one form in a population or a gene that is found as only one allele in a 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
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
In order to derive the Hardy-Weinberg equation, the two scientists assumed that _________ the population's gene pool.
gametes are independently chosen at random from
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
Allele Frequencies
the number of copies of a particular allele in a population divided by the total number of alleles in that population
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
Hardy-Weinberg Equilibrium
the phenomenon by which, under certain conditions, allele frequencies are maintained in a stable condition and genotypes can be predicted according to the Hardy-Weinberg equation
Inbreeding Depression
the phenomenon in which inbreeding produces homozygotes that are less fit, thereby decreasing the reproductive success of a population
