12/13/23, 5:40 PM Final Assessment Answer Key: BIO220H1 S LEC0101 20211:From Genomes to Ecosystems in a Changing World
Final Assessment Answer Key
Imagine a hypothetical species in which males disperse from the habitat they were born into and
breed elsewhere, but females remain in the habitat in which they were born and reproduce in that
location. What would be the correct ranking of Fst values for loci on the Y chromosome, mtDNA, and
an autosome?
A. Y chromosome Fst > mtDNA Fst > autosome Fst
B. Autosome Fst > Y chromosome Fst > mtDNA Fst
C. mtDNA Fst > autosome Fst > Y chromosome Fst
D. mtDNA Fst = Y chromosome Fst = autosome Fst
A researcher studied resistance to parasites in various lines of the legume plant Medicago truncatula.
One of her genetic lines of M. truncatula was significantly more resistant to the parasite than the
other lines, so she decided to sequence the DNA of each line. She identified a mutation that
appeared to be responsible for the increased resistance (white star; Figure 1), as well as several
other neutral genetic mutations in that region (black stars). After being exposed to selective pressure
by parasites over many generations, the researcher sequenced the DNA of the current population of
plants (Figure 2). Which statement is the BEST interpretation of her results, AND how would these
results change if recombination is occurring? (In both figures, one horizontal line represents the DNA
sequence of one plant).
A. An incomplete sweep has occurred; recombination should decrease genetic variation around the
beneficial mutation.
B. Genetic hitchhiking has occurred; recombination should not change genetic variation around the
beneficial mutation.
C. A complete sweep has occurred; recombination should increase genetic variation around the
beneficial mutation.
, 12/13/23, 5:40 PM Final Assessment Answer Key: BIO220H1 S LEC0101 20211:From Genomes to Ecosystems in a Changing World
D. An incomplete sweep has occurred; recombination should increase genetic variation
around the beneficial mutation.
You have sequenced a population of previously undiscovered elephants you found on a densely
forested island. These new elephants have 750 single nucleotide polymorphisms (SNPs) with
significantly higher frequencies relative to the mainland elephants. What is the MOST likely
explanation for this?
A. The island elephants have undergone a population bottleneck when this new population
established
B. Genetic hitchhiking - a beneficial mutation has dragged the other SNPs along as it increased in
frequency
C. The island elephants have increased phenotypic plasticity relative to the mainland elephants.
D. The island elephants have experienced polygenic adaptation to a new environment
Final Assessment Answer Key
Imagine a hypothetical species in which males disperse from the habitat they were born into and
breed elsewhere, but females remain in the habitat in which they were born and reproduce in that
location. What would be the correct ranking of Fst values for loci on the Y chromosome, mtDNA, and
an autosome?
A. Y chromosome Fst > mtDNA Fst > autosome Fst
B. Autosome Fst > Y chromosome Fst > mtDNA Fst
C. mtDNA Fst > autosome Fst > Y chromosome Fst
D. mtDNA Fst = Y chromosome Fst = autosome Fst
A researcher studied resistance to parasites in various lines of the legume plant Medicago truncatula.
One of her genetic lines of M. truncatula was significantly more resistant to the parasite than the
other lines, so she decided to sequence the DNA of each line. She identified a mutation that
appeared to be responsible for the increased resistance (white star; Figure 1), as well as several
other neutral genetic mutations in that region (black stars). After being exposed to selective pressure
by parasites over many generations, the researcher sequenced the DNA of the current population of
plants (Figure 2). Which statement is the BEST interpretation of her results, AND how would these
results change if recombination is occurring? (In both figures, one horizontal line represents the DNA
sequence of one plant).
A. An incomplete sweep has occurred; recombination should decrease genetic variation around the
beneficial mutation.
B. Genetic hitchhiking has occurred; recombination should not change genetic variation around the
beneficial mutation.
C. A complete sweep has occurred; recombination should increase genetic variation around the
beneficial mutation.
, 12/13/23, 5:40 PM Final Assessment Answer Key: BIO220H1 S LEC0101 20211:From Genomes to Ecosystems in a Changing World
D. An incomplete sweep has occurred; recombination should increase genetic variation
around the beneficial mutation.
You have sequenced a population of previously undiscovered elephants you found on a densely
forested island. These new elephants have 750 single nucleotide polymorphisms (SNPs) with
significantly higher frequencies relative to the mainland elephants. What is the MOST likely
explanation for this?
A. The island elephants have undergone a population bottleneck when this new population
established
B. Genetic hitchhiking - a beneficial mutation has dragged the other SNPs along as it increased in
frequency
C. The island elephants have increased phenotypic plasticity relative to the mainland elephants.
D. The island elephants have experienced polygenic adaptation to a new environment
