Before Lesson 13 Quiz genetic drift

A dwindling population of 1000 frogs occupies an isolated watershed in Costa Rica. To help preserve the species, scientists caught 20 frogs to start a new population in a nearby watershed. This species has a gene that affects eye shape. The 1000-member wild population has two alleles for this gene: R and r, with frequencies 0.7 and 0.3, respectively. What will be the allele frequencies of R and r in the 20-member founder population?

A) The frequencies will be 0.7 for R and 0.3 for r.

B) The founder populations' allele frequencies will necessarily be different than the source population's frequencies.

C) The frequencies will be 1.0 for R and 0 for r.

D) The expected frequencies are 0.7 for R and 0.3 for r. The actual frequencies could be different.

D) The expected frequencies are 0.7 for R and 0.3 for r. The actual frequencies could be different.

Which one of the following best defines the founder effect?

 

A) Sampling error that occurs during the establishment of a new population by a small number of migrants.

B) Strong natural selection acting on the founders of a new population because the environment they are now living in is so different from the environment they came from.

C) A phenomenon named after William Founder, who observed that top predators generally have low genetic diversity.

D) Rapid population growth following a bottleneck.

A) Sampling error that occurs during the establishment of a new population by a small number of migrants.

True or false? "The effects of genetic drift are more pronounced in smaller populations."

A) True

B) False

A) True

True or false? If genetic drift is occurring in a population then the population can also be in Hardy-Weinberg equilibrium.

A) True

B) False

B) False

If gametes from a gene pool combine randomly to make only a small number of zygotes, the allele frequencies among the zygotes may be different than they were in the gene pool because:

 

A) The effects of natural selection are more pronounced in small populations.

B) The effects of sampling error are more pronounced with small samples.

C) The effects of genetic drift over several generations are more pronounced with small numbers of gametes.

D) The effects of differences in frequencies for different alleles are more pronounced with small numbers of zygotes.

B) The effects of sampling error are more pronounced with small samples.

This is a synthesis question, asking you to think about both genetic drift and other mechanisms of evolution you've learned about so far.

Which of the following statements best completes this statement? "Genetic drift is different from natural selection because...:"

 

A) In natural selection allele frequencies change because some alleles confer higher fitness, whereas in genetic drift allele frequencies change because of chance sampling error.

B) Natural selection acts primarily in large populations, whereas genetic drift acts primarily in small ones.

C) Natural selection is a mechanism of evolution, whereas genetic drift is an outcome of evolution.

D) Natural selection tends to cause rapid evolution, whereas genetic drift tends to cause slow evolution.

A) In natural selection allele frequencies change because some alleles confer higher fitness, whereas in genetic drift allele frequencies change because of chance sampling error.

The frequency of an allele -- let's call it D -- in a population moves to either a frequency of 0 or a frequency of 1 what does this mean over time for the D allele?

A) When the frequency of D is zero it is lost from the population; when the frequency of D is 1 it is the only allele in the population.

B) When the frequency of D is zero it is fixed in population; when the frequency of D is 1 it is lost from the population.

C) Regardless of it's frequency, D will always make up 50% of the alleles in the population.

D) It means that D will always be the least frequent in the population.

A) When the frequency of D is zero it is lost from the population; when the frequency of D is 1 it is the only allele in the population.

What happens to allele frequencies when small population size persists over many generations? Exclude other evolutionary mechanisms when considering this question.

A) We predict all alleles will be lost from the population.

B) We predict that one allele will become fixed in the population, but we cannot predict which one.

C) We can predict exactly which allele will become fixed in a small population.

B) We predict that one allele will become fixed in the population, but we cannot predict which one.

When genetic drift is the only evolutionary force acting on a small population, what happens to genetic variation within a population?

A) Over time, individuals in the population are more genetically similar to each other.

B) Over time, individuals in the population are less genetically similar to each other.

C) Over time, the genetic variance between individuals in the population does not change.

A) Over time, individuals in the population are more genetically similar to each other.

Genetic drift is acting independently on every gene at every locus in a genome. Does genetic drift acting in Population A make the population more or less phenotypically similar to Population B where genetic drift is also acting? Exclude all other evolutionary mechanisms for this question.

A) Genetic drift makes the two populations less phenotypically similar to each other.

B) Genetic drift makes the two populations more phenotypically similar to each other.

C) Genetic drift alone will not affect the phenotypic differences between the two populations.

A) Genetic drift makes the two populations less phenotypically similar to each other.