Population Genetics

The frequency of two alleles, Q and q, is 0.2 and 0.8, respectively. What is the frequency of Qq heterozygotes in this population?

0.16, 0.32

Assuming that p = 0.3 for a population in Hardy-Weinberg equilibrium, what would be the expected frequency of heterozygotes for the involved allelic pair?

0.42

Given an inheritance pattern of incomplete dominance and 81 flowers that are red (R1R1), 18 flowers that are pink (R1R2), and 1 flower that is white (R2R2), what is the frequency of the R1 allele?

0.9

For a given locus, in a population with two alternative alleles, the allele frequencies p + q = ________.

1

Suppose that a given gene undergoes a mutation to a dominant allele such that 2 out of 100,000 offspring exhibit the new mutant phenotype. Assuming that these offspring are heterozygous, what is the mutation rate for the gene?

1/100,000

If the frequency of the disorder in the population is 0.0056, what is the percentage of heterozygous carriers?

13.8%

In a population that meets the Hardy-Weinberg equilibrium assumptions, 81% of the individuals are homozygous for a recessive allele. What percentage of the individuals would be expected to be heterozygous for this locus in the next generation?

18%

In a population of cattle, the following color distribution was noted: 36% red (RR), 48% roan (Rr), and 16% white (rr). This population is in a Hardy-Weinberg equilibrium. What will be the distribution of genotypes in the next generation if the Hardy-Weinberg assumptions are met?

36% red; 48% roan; 16% white

In a population of 100 individuals, 49% are of the NN blood type. What percentage is expected to be MN assuming Hardy-Weinberg equilibrium conditions?

42%

Assume that in a Hardy-Weinberg population, 9% of the individuals are of the homozygous recessive phenotype. What percentage are homozygous dominant?

49%

Albinism is an autosomal recessive trait in humans. Assume that there are 100 albinos (aa) in a population of 1 million. How many individuals would be expected to be homozygous normal (AA) under equilibrium conditions?

980,000

What is genetic equilibrium?

A condition for a population in which the frequency of given alleles remains constant from generation to generation.

A population of cheetahs was hunted to near extinction during the last three decades of the 19th century. The number of animals increased to pre-19th century levels due to their location being made off limits to hunters during the latter half of the 20th century. Albinism, which was previously rare in this population, is now 10-fold over the frequency observed prior to the near extinction event. This is an example of

A genetic bottleneck

How do we know whether the genetic structure of a population is static or dynamic?

By conducting assays of allele and/or genotypic frequencies over time and space, one can determine whether the genetic structure of a population is changing.

One of the Hardy-Weinberg assumptions states that all genotypes in the population are free of selective advantage. What influence might a selective advantage of a genotype have on a Hardy-Weinberg equilibrium?

Certain alleles will reach the next generation on a nonrandom basis, thus upsetting the equilibrium.

What is required for speciation to occur?

Changes in reproductive behavior

What is macroevolution?

Evolutionary events leading to the emergence of new species and other taxonomic groups

How do geneticists detect presence of genetic variation as different alleles in a population?

Different alleles will show typical segregation patterns, and although they will have similar nucleotide and amino acid sequences, some differences will exist between them

True or false: Negative assortative mating occurs when similar genotypes are allowed to mate.

False

What are the genetic consequences of inbreeding?

For a given allele, inbreeding increases the proportion of homozygotes in a population.

Would one expect a linear relationship between DNA sequence divergence and phylogenetic distance?

Not necessarily, because some sections of DNA evolve more slowly if they code for products that serve important cellular functions, whereas other sections without such constraints evolve more quickly

What term is given to the total genetic information carried by all members of a population?

Gene pool

A number of mechanisms operate to maintain genetic diversity in a population. Why is such diversity favored?

Genetic diversity may better adapt a population to inevitable changes in the environment

How do we know how much genetic variation is in a population?

Genetic variation can be assessed in a variety of ways including responses to artificial selection and sequencing of nucleic acids and proteins

Which of the following statements best describes the relationship between the Hardy-Weinberg principle and the effects of natural selection?

If selection can be quantified, relative fitness values can be calculated and used to appropriately modify the Hardy-Weinberg equation.

Speciation

The process of splitting a genetically homogeneous population into two or more populations that undergo genetic differentiation and eventual reproductive isolation

Cytochrome c is a respiratory pigment found in the mitochondria of eukaryotes. Compared with some other proteins, it has changed very slowly over long periods of time. Why?

It serves a vital function; therefore, any changes in amino acid sequence are usually strongly selected against

In a population of 10,000 individuals, where 3600 are MM, 1600 are Mm, and 4800 are mm, what are the frequencies of the M alleles and the m alleles?

M = 0.6; m = 0.4

Which types of nucleotide changes (missense or synonyms) cause amino acid changes?

Missense mutations causes amino acid changes.

What information have the results of mitochondrial DNA analysis offered concerning the phylogenetic relationships between Neanderthals and modern humans?

Neanderthals and humans share a common ancestor Neanderthals were a separate hominid line Neanderthals did not contribute mitochondrial genes to H. sapiens

What is the term given to a group of individuals belonging to the same species that live in a defined geographic area that actually or potentially interbreed?

Population

One of the Hardy-Weinberg assumptions states that the population is infinitely large. What influence might a small population size have on the Hardy-Weinberg equilibrium?

Sampling error would cause random and possibly significant fluctuations in determination of gene frequencies

Which of the following statements best describes the relationship between fitness and selection coefficient (s)?

The stronger the selection against a given genotype, the lower the fitness associated with that genotype.

What is meant by the equation p + q = 1.0?

The sum of relevant individual alleles in a population is equal to 100% of those alleles.

What are phylogenetic trees?

a diagrammatic representations of evolutionary relationships among organisms

Which factor contributes to the phenomenon of natural selection?

competition for survival

Which of the following does not change gene frequencies in populations?

diet

Natural selection occurs when there is nonrandom elimination of genotypes from a population due to

differences in viability or reproductive success

You collect samples of a population of bacteria which exists near hydrothermal vents on the ocean floor. Temperatures near the vents average 80°C, while a few meters away the temperature is only a few degrees above freezing. You find that the majority of bacteria in your samples require temperatures near either of those extremes to grow. Which of the following types of selection appear to be acting on this population?

disruptive selection

Which method is often used to analyze proteins and nucleic acids by physical separation when estimating genetic variation in populations?

electrophoresis

What does the variable 2pq represent?

expected frequency of heterozygotes in a population in the Hardy−Weinberg equilibrium

Which term is given to the measure of the proportion of offspring that a particular phenotype will contribute to the next generation?

fitness

Inbreeding will change

gene frequencies

Evolution is dependent on ________ in the evolving population.

genetic diversity

In small isolated populations, gene frequencies can fluctuate considerably. The term that applies to this circumstance is ________.

genetic drift

Which natural factors affect changes in genetic variation?

genetic drift crossing over migration chromosomal assortment selection

In zoo animals, inbreeding often occurs because of a lack of a sufficient pool of breeding individuals. Under such conditions, what two characteristics are often exhibited among inbred organisms?

higher mortality rates & higher frequency of aberrant phenotypes

Conservation of amino acid sequence among distantly related groups of organisms is suggestive of a(n)

important function for that sequence

Selection

is regarded as a strong evolutionary mechanism for changing allelic frequencies

Genetic drift arises from all the following EXCEPT

mutations

Mutation and migration introduce new alleles into populations. What is the most likely principal force that will shift allelic frequencies within large populations?

natural selection

Which assumption pertains to a population in a Hardy-Weinberg equilibrium?

no migration, mutation or, genetic drift

Two species that have experienced several thousand years of isolation from one another are now incapable of producing viable offspring despite mating efforts. What type of reproductive isolating mechanism developed between the two species?

postzygotic mechanisms

What is meant by horizontal transfer?

process of passing genetic information from one organism to another without producing offspring.

According to the neutral theory of evolution, the diversity of alleles at most loci is the result of

random genetic drift

Which general term is used to group various biological and behavioral properties of organisms that act to prevent or reduce interbreeding?

reproductive isolating mechanisms

What single event is probably common to all occurrences of speciation?

reproductive isolation

What is the differential reproduction of genotypes, resulting from their variable fitness?

selection

Which would change allele frequencies more quickly: selection against a dominant allele or selection against a recessive allele?

selection against a dominant allele

Selection that favors the middle phenotype and selects against the extreme phenotypes is said to be ________.

stabilizing selection

Which of the following is NOT characteristic of the ideal population on which the Hardy-Weinberg law is based?

subject to mutation

In the case of complete dominance in a population in equilibrium, we cannot tell which individuals are homozygous dominants and which are heterozygous, what information is needed to determine the frequency of homozygous dominant and heterozygous genotypes?

the frequency of homozygous recessive genotype

A rationale for using DNA sequence polymorphisms as an index of genetic diversity

there may be a general relationship between genetic diversity and evolutionary diversity.

Directional selection generates a phenotypic shift ________.

toward an extreme of the phenotype

True or false: Paleogenomics is based on the recovery and sequencing of DNA from fossil remains of extinct species

true

Genetic drift is primarily associated with what size breeding populations?

very small