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Genetic hitchhiking describes a phenomenon wherein an allele's frequency alteration is not a direct consequence of selection acting upon it, but rather due to its linkage with another genetic locus experiencing a selective sweep.
Answer: True
Genetic hitchhiking occurs when an allele's frequency changes not due to direct selection, but because it is physically linked to another gene that is undergoing a selective sweep.
A selective sweep is initiated by a newly arisen mutation that is disadvantageous, leading to its rapid decrease in frequency.
Answer: False
A selective sweep is initiated by an advantageous mutation, which increases rapidly in frequency, not a disadvantageous one.
Neutral or even slightly disadvantageous alleles may be influenced by genetic hitchhiking if they are in close physical proximity to a beneficial mutation undergoing selection.
Answer: True
The phenomenon of genetic hitchhiking can indeed impact alleles that are neutral or even slightly disadvantageous, provided they are physically linked to a beneficial mutation experiencing positive selection.
During a selective sweep, alleles physically linked to the advantageous mutation experience an increase in frequency, whereas alleles linked to non-advantageous versions experience a decrease.
Answer: True
In the context of a selective sweep, alleles that are linked to the advantageous mutation will rise in frequency, while those linked to non-advantageous alleles will decline.
Genetic hitchhiking typically leads to an augmentation of genetic variation within a population.
Answer: False
Genetic hitchhiking generally results in a reduction, not an increase, of genetic variation within a population due to the linked alleles being carried along with the selected mutation.
An allele undergoing hitchhiking alongside a beneficial mutation may possess its own selective value, being neutral, advantageous, or deleterious.
Answer: True
The allele that hitchhikes does not need to be neutral; it can possess its own selective advantage, disadvantage, or be neutral with respect to fitness.
What is the principal mechanism underlying genetic hitchhiking?
Answer: An allele's frequency changing due to its linkage with another gene undergoing a selective sweep.
The primary mechanism involves an allele's frequency shifting not due to direct selection upon itself, but as a consequence of its physical linkage to another allele that is experiencing strong positive selection (a selective sweep).
According to the provided text, what event initiates a selective sweep?
Answer: A newly arisen mutation that is advantageous.
A selective sweep is initiated by the emergence and rapid proliferation of a beneficial mutation within the population.
What is the typical consequence of genetic hitchhiking for the genetic diversity observed within a population?
Answer: It leads to a reduction in genetic diversity.
Genetic hitchhiking typically results in a decrease in genetic diversity, as linked neutral or deleterious alleles are swept along with the positively selected allele, reducing variation at nearby loci.
Which of the following terms is NOT cited in the source as an alternative name for genetic hitchhiking?
Answer: Background selection
While 'genetic draft' and 'hitchhiking effect' are presented as synonyms for genetic hitchhiking, 'background selection' refers to a distinct, though related, evolutionary process.
Genetic draft is posited as an alternative designation for genetic hitchhiking, implying an identical underlying mechanism.
Answer: True
The terminology 'genetic draft' is often employed synonymously with 'genetic hitchhiking,' denoting the same evolutionary process.
Background selection and genetic hitchhiking are classified as non-stochastic evolutionary forces, implying predictability.
Answer: False
Both background selection and genetic hitchhiking are considered stochastic (random) evolutionary forces, akin to genetic drift, rather than deterministic or predictable ones.
Genetic drift and genetic draft share a similarity in that both are classified as stochastic, or random, evolutionary processes.
Answer: True
Both genetic drift and genetic draft are fundamentally stochastic processes, meaning their outcomes are influenced by chance events rather than deterministic selective pressures.
The impact of genetic drift is amplified in larger populations due to the presence of N in the denominator of the variance formula.
Answer: False
The variance formula for genetic drift (pq / 2N) indicates that the impact of drift is inversely proportional to population size; thus, it is greater in smaller populations, not larger ones.
Frequency changes resulting from genetic draft are independent across generations, in contrast to genetic drift effects, which are autocorrelated.
Answer: False
Frequency changes due to genetic drift are independent between generations, while genetic draft effects exhibit autocorrelation, meaning they tend to persist or amplify across generations.
Genetic draft generates an allele frequency spectrum that is identical to that produced by genetic drift.
Answer: False
Genetic draft and genetic drift do not produce identical allele frequency spectra; they differ in their characteristic distributions of allele frequencies.
Stochastic processes within evolutionary biology are characterized by randomness and unpredictability.
Answer: True
Stochastic evolutionary processes are fundamentally driven by chance, leading to outcomes that are inherently random and unpredictable.
In what fundamental way does genetic draft differ from genetic drift?
Answer: Genetic drift affects allele frequencies through sampling error, while genetic draft is driven by linkage to selected alleles.
Genetic drift operates via random sampling error in allele frequencies across generations, whereas genetic draft's influence on allele frequencies stems from linkage disequilibrium with alleles undergoing selection.
How do the allele frequency changes induced by genetic draft compare to those resulting from genetic drift?
Answer: Draft changes are autocorrelated between generations, while drift changes are independent.
Frequency changes driven by genetic drift are independent from one generation to the next, whereas changes due to genetic draft exhibit autocorrelation, tending to persist across generations.
Which term denotes the random fluctuation of allele frequencies from one generation to the next, resulting from sampling error?
Answer: Genetic drift
Genetic drift is the term used to describe the random changes in allele frequencies within a population from one generation to the next, primarily caused by sampling error during reproduction.
What is the defining characteristic of a stochastic process in evolutionary biology?
Answer: It involves randomness and chance, with unpredictable outcomes.
Stochastic processes in evolution are characterized by the involvement of randomness and chance, leading to outcomes that are not predetermined and can vary unpredictably.
Genetic recombination acts to prevent genetic hitchhiking by disrupting the linkage between selected and non-selected alleles.
Answer: True
Genetic recombination is a crucial factor that can interrupt genetic hitchhiking by breaking the physical linkage between the selected locus and nearby alleles.
The hitchhiking effect is more pronounced when the linked polymorphism is physically distant from the selected gene, facilitating greater recombination.
Answer: False
The hitchhiking effect is generally weaker when the linked polymorphism is physically distant from the selected gene, as increased recombination breaks the linkage. Conversely, proximity strengthens the effect.
The Y chromosome exhibits particular susceptibility to genetic hitchhiking due to its lack of genetic recombination.
Answer: True
The absence of genetic recombination on the Y chromosome renders it highly susceptible to genetic hitchhiking, as linkage disequilibrium is maintained over larger genomic regions.
Genetic hitchhiking occurring on the Y chromosome is proposed as an explanatory factor for the relatively diminished number of functional genes observed on it.
Answer: True
The process of genetic hitchhiking on the non-recombining Y chromosome is hypothesized to contribute to its relatively low complement of functional genes.
Which of the following mechanisms can interrupt or mitigate the process of genetic hitchhiking?
Answer: Genetic recombination.
Genetic recombination serves as a primary mechanism that can interrupt genetic hitchhiking by breaking the physical linkage between the selected allele and nearby hitchhiking alleles.
How does the physical distance between a polymorphism and a gene undergoing selection influence the process of genetic hitchhiking?
Answer: Closer proximity strengthens the effect by reducing recombination opportunities.
Closer physical proximity between a polymorphism and a selected gene strengthens the hitchhiking effect because it reduces the likelihood of recombination breaking the linkage between them.
What characteristic of the Y chromosome contributes to its particular susceptibility to genetic hitchhiking?
Answer: It lacks genetic recombination entirely.
The Y chromosome's lack of genetic recombination is the primary reason for its heightened susceptibility to genetic hitchhiking, as linkage disequilibrium is maintained over extensive chromosomal regions.
What evolutionary hypothesis concerning the Y chromosome's gene content is proposed by the phenomenon of genetic hitchhiking?
Answer: It proposes hitchhiking contributes to the relatively low number of functional genes on the Y chromosome.
Genetic hitchhiking provides a potential explanation for the observation of a relatively low number of functional genes on the Y chromosome, possibly due to the accumulation of linked deleterious mutations.
What is the relationship between the rate of genetic recombination and the extent of genetic hitchhiking?
Answer: Higher recombination rates break down linkage disequilibrium, limiting the distance over which hitchhiking occurs.
Higher rates of genetic recombination tend to limit the extent of genetic hitchhiking because recombination disrupts linkage disequilibrium, thereby reducing the genomic distance over which alleles are co-inherited.
The term 'hitchhiking' within the field of genetics was initially proposed in 1974 by the researchers John Maynard Smith and John Haigh.
Answer: True
The seminal work introducing the concept of genetic hitchhiking was published in 1974 by John Maynard Smith and John Haigh.
John H. Gillespie is identified as the principal researcher credited with coining the term 'hitchhiking' in genetics.
Answer: False
While John H. Gillespie made significant contributions to the study of genetic hitchhiking, the term itself was initially introduced by John Maynard Smith and John Haigh.
Patterns of reduced genetic variation proximal to selective sweeps, a consequence of hitchhiking, are utilized by researchers to identify genes that have undergone recent selection.
Answer: True
The characteristic reduction in genetic variation observed near selective sweeps, attributable to hitchhiking, serves as a valuable signature for identifying genes that have been under recent positive selection.
Genetic hitchhiking is considered a prerequisite for the evolution of increased mutation rates (mutators) to be favored by selection acting upon evolvability.
Answer: True
Genetic hitchhiking plays a crucial role in enabling the evolution of mutator genes, facilitating their selection by increasing the rate of beneficial mutations.
Genetic recombination disrupts the linkage between a mutator gene and beneficial mutations, thereby diminishing the likelihood of mutator spread.
Answer: True
The process of genetic recombination can indeed disrupt the linkage between a mutator gene and beneficial mutations, consequently reducing the probability of the mutator's fixation.
The evolution of mutators is anticipated to be less prevalent in asexual species due to the inability of recombination to separate them from beneficial mutations.
Answer: False
The evolution of mutators is generally expected to be *more* common in asexual species, precisely because the absence of recombination prevents their separation from beneficial mutations.
Genetic hitchhiking presents a challenge to the neutral theory of molecular evolution by offering a mechanism through which selection influences allele fixation.
Answer: True
Genetic hitchhiking challenges the tenets of the neutral theory of molecular evolution by demonstrating a pathway through which selection can drive the fixation of alleles, even those not directly selected.
The McDonald-Kreitman test serves to detect evidence of positive selection through the comparative analysis of polymorphism and divergence patterns.
Answer: True
The McDonald-Kreitman test is a statistical method employed to detect positive selection by comparing patterns of genetic polymorphism within a species to patterns of divergence between species.
A mutator gene is defined by its capacity to elevate the mutation rate in other genes.
Answer: True
A mutator gene is characterized by its function of increasing the rate at which mutations occur in the broader genome.
What is a key application derived from studying the patterns generated by genetic hitchhiking?
Answer: To identify genes that have been under very recent positive selection.
A significant application involves using the signature of reduced genetic variation near selective sweeps, caused by hitchhiking, to identify genes that have experienced recent positive selection.
For the evolution of increased mutation rates (mutators) to be favored by selection acting on evolvability, what factor is considered necessary?
Answer: Genetic hitchhiking.
Genetic hitchhiking is considered a necessary condition for the selection of mutator genes, as it facilitates their spread when they increase the rate of beneficial mutations.
What is the impact of genetic recombination on the spread of mutator genes?
Answer: Recombination disrupts the linkage, making the spread of mutators less likely.
Genetic recombination disrupts the physical linkage between a mutator gene and any beneficial mutations it facilitates, thereby reducing the probability of the mutator's spread and fixation.
What is the reason mutator genes are generally expected to evolve more readily in asexual species?
Answer: The absence of recombination in asexual species prevents the separation of mutators from beneficial mutations they help create.
In asexual species, the lack of recombination prevents the separation of mutator genes from beneficial mutations they facilitate, thereby promoting their evolution and spread.
In what manner does genetic hitchhiking challenge the neutral theory of molecular evolution?
Answer: By showing that selection can explain allele fixation even for non-selected alleles.
Genetic hitchhiking challenges the neutral theory by illustrating how selection acting on one locus can lead to the fixation of alleles at linked, non-selected loci, suggesting a greater role for selection in molecular evolution than proposed by the neutral theory.
What is the primary objective of the McDonald-Kreitman test within evolutionary genetics?
Answer: To detect evidence of positive selection.
The primary purpose of the McDonald-Kreitman test is to detect evidence of positive selection by comparing the number of synonymous and non-synonymous substitutions between species with the number of synonymous and non-synonymous polymorphisms within a species.
What is the definition of a mutator gene?
Answer: A gene that increases the rate at which mutations occur in other genes.
A mutator gene is defined by its property of elevating the mutation rate in other genes within the genome.
In biology, what does the term 'evolvability' refer to?
Answer: The capacity of a system to generate evolutionary novelty and adapt over time.
Evolvability refers to the inherent capacity of a biological system or lineage to generate novel adaptations and evolve over time in response to environmental pressures.
What is the central tenet of the neutral theory of molecular evolution?
Answer: Most evolutionary changes at the molecular level are caused by the random fixation of neutral mutations through genetic drift.
The central tenet of the neutral theory of molecular evolution posits that the majority of evolutionary changes at the molecular level are attributable to the random fixation of neutral mutations via genetic drift, rather than positive selection.
In idealized populations of size N, the variance in allele frequency attributable to genetic drift is mathematically represented by the formula pq / (2N).
Answer: True
The variance in allele frequency resulting from genetic drift in idealized populations of effective size N is indeed quantified by the expression pq / (2N), where p and q represent allele frequencies.
The effective population size relevant to genetic draft may diverge substantially from the actual census population size.
Answer: True
Effective population size, a critical parameter in population genetics, often differs from the census size due to factors influencing reproductive success and genetic contribution, and this distinction is relevant for processes like genetic draft.
Linkage disequilibrium signifies that alleles are *not* inherited independently; rather, they tend to be inherited together due to their close physical proximity on a chromosome.
Answer: False
Linkage disequilibrium indicates that alleles are *not* inherited independently; rather, they tend to be inherited together due to their close physical proximity on a chromosome.
A polymorphism is defined as the presence of two or more common variants of a gene or DNA sequence within a population.
Answer: True
In population genetics, a polymorphism denotes the occurrence of two or more distinct forms (alleles or DNA sequences) at a particular locus within a population, with each form present at a frequency greater than typically expected by mutation alone.
Effective population size is a theoretical construct that often differs significantly from the census population size, reflecting factors that influence the rate of genetic drift.
Answer: False
Effective population size is a theoretical construct that often differs significantly from the census population size, reflecting factors that influence the rate of genetic drift.
Based on the formula pq / (2N), how does population size (N) influence the magnitude of genetic drift's impact?
Answer: Smaller populations experience stronger drift.
The formula pq / (2N) demonstrates that the variance due to genetic drift is inversely proportional to population size (N), meaning drift is more potent in smaller populations.
What is the meaning of linkage disequilibrium in the context of genetics?
Answer: Alleles are inherited together more often than by chance, usually due to close physical proximity on the same chromosome.
Linkage disequilibrium signifies a non-random association between alleles at different loci, meaning they are inherited together more frequently than expected by chance, typically because they are physically close on the same chromosome.
Within the context of population genetics, what is the definition of a polymorphism?
Answer: The existence of two or more common forms of a gene or DNA sequence within a population.
A polymorphism refers to the presence of multiple common variants (alleles or DNA sequences) for a specific gene or DNA region within a population.
What implication arises from the variance formula pq / (2N) concerning genetic drift?
Answer: Drift's effect is inversely proportional to population size (N).
The formula pq / (2N) implies that the magnitude of allele frequency variance due to genetic drift is inversely proportional to the population size (N), meaning drift is more potent in smaller populations.
What is the precise definition of allele frequency?
Answer: The relative proportion of a specific allele within a population's gene pool.
Allele frequency quantifies the relative occurrence of a particular allele (a variant of a gene) within the gene pool of a population.
What is the definition of effective population size?
Answer: A theoretical size of an idealized population experiencing the same rate of genetic drift as the actual population.
Effective population size (Ne) is a theoretical measure representing the size of an idealized population that would experience the same magnitude of random genetic drift as the actual population under study.
What does an allele frequency spectrum represent?
Answer: The distribution of frequencies of all alleles present within a population or sample.
An allele frequency spectrum graphically depicts the distribution of frequencies for all alleles found within a given population or sample.
How does linkage disequilibrium facilitate the process of genetic hitchhiking?
Answer: By keeping alleles physically linked on a chromosome, allowing them to be inherited together.
Linkage disequilibrium enables genetic hitchhiking by maintaining the physical association of alleles on a chromosome, ensuring they are inherited together and thus their frequencies change in concert with a selected allele.