Module 03 Quiz: Molecular Evolution

Which type of nucleotide substitution is LEAST likely to be neutral (i.e. not under selection)?

Correct answer:

A) Non-synonymous

B) Non-coding

C) Synonymous

D) Orthologous

A) Non-synonymous

Which of the following best explains variation in genome size?

A) Transposable elements

B) Number of genes

C) Non-synonymous mutations

D) Number of pseudogenes

A) Transposable elements

Match each Ka/Ks ratio with its correct interpretation. (Ka/Ks = 1 , Ka/Ks < 1 , Ka/Ks > 1)

purifying/ negative selection, positive selection, neutral evolution

Ka/Ks = 1 neutral evolution

Ka/Ks < 1 purifying/ negative selection

Ka/Ks > 1 positive selection

Which is true of frame shift indels?

A) usually deleterious

B) usually result in adaptation

C) maintain the open reading frame but shifted one or more codons

D) insertion or deletion of a multiple of 3 base pairs

A) usually deleterious

To calculate Ka/Ks we must compare ______________ sequences.

A) Duplicated

B) Neutral

C) Orthologous

D) Paralogous

C) Orthologous

Approximately how much of the human genome consists of functional protein coding sequence?

(Choose the closest value)

A) less than 98%

B) less than 25%

C) less than 10%

D) less than 2%

E) less than 50%

D) less than 2%

The last common ancestor of Species 1, Species 2, and Species 3 had two genes (Gene A and Gene B) that arose by gene duplication. Gene B is a duplicate of Gene A. When Species 1, 2, and 3 evolved from this common ancestor, each one inherited Gene A and Gene B so that:

Species 1 carries Gene A1 and Gene B1

Species 2 carries Gene A2 and Gene B2

Species 3 carries Gene A3 and Gene B3

In this scenario, Genes A2 and A3 are

A) Transposons

B) Orthologs

C) Paralogs

D) Neutral genes

B) Orthologs

Match the evolutionary force with its expected "footprint" on genomic variation.

Genomic variation:

-Migration

-Random Genetic Drift

-Natural Selection

Evolutionary force:

-Genome wide differences in allele frequencies (variation) among populations

-Reduced nucleotide variation, but only for the gene under selection

-Genome wide reduction in variation

Migration - Genome wide differences in allele frequencies (variation) among populations

Random Genetic Drift - Genome wide reduction in variation

Natural Selection - Reduced nucleotide variation, but only for the gene under selection

The last common ancestor of Species 1, Species 2, and Species 3 had two genes (Gene A and Gene B) that arose by gene duplication. Gene B is a duplicate of Gene A. When Species 1, 2, and 3 evolved from this common ancestor, each one inherited Gene A and Gene B so that:

Species 1 carries Gene A1 and Gene B1

Species 2 carries Gene A2 and Gene B2

Species 3 carries Gene A3 and Gene B3

In this scenario, Genes A1 and A2 are

A) Paralogs

B) Orthologs

C) Duplicates

B) Orthologs

The last common ancestor of Species 1, Species 2, and Species 3 had two genes (Gene A and Gene B) that arose by gene duplication. Gene B is a duplicate of Gene A. When Species 1, 2, and 3 evolved from this common ancestor, each one inherited Gene A and Gene B so that:

Species 1 carries Gene A1 and Gene B1

Species 2 carries Gene A2 and Gene B2

Species 3 carries Gene A3 and Gene B3

In this scenario, Genes A3 and B3 are

A) Transposons

B) Neutral genes

C) Orthologs

D) Paralogs

D) Paralogs

Based on the following two gene sequences, what can you infer about the influence of natural selection? (Assume all 1st and 2nd position are non-synonymous and all 3rd positions are synonymous)

Species 1 - ATG AAT TTC GTC ACG

Species 2 - ATG TTC CTA ATC ACG

A) The gene is under positive selection

B) The gene is not under selection (evolving neutrally)

C) The gene is under purifying selection

B) The gene is not under selection (evolving neutrally)

What is the most common fate of new gene duplicates?

A) Sub-functionalization

B) Pseudogenization

C) Neo-functionalization

D) All are equally likely

B) Pseudogenization

Match each theory with its defining features.

Theories:

-Selectionist Theory

-Neutral Theory

-Nearly-neutral Theory

Features:

-Natural selection is the dominant driver of evolutionary change in DNA sequences

-Most mutations have a small beneficial or deleterious effect

-Most mutations have no effect on fitness

-All mutations have a beneficial or deleterious effect

-Genetic drift is the dominant force driving evolutionary change in DNA sequences

-Population size affects the relative importance of natural selection versus genetic drift in driving evolutionary change in DNA sequences

Selectionist Theory:

-Natural selection is the dominant driver of evolutionary change in DNA sequences

-All mutations have a beneficial or deleterious effect

Neutral Theory:

-Genetic drift is the dominant force driving evolutionary change in DNA sequences

-Most mutations have no effect on fitness

Nearly-neutral Theory:

-Most mutations have a small beneficial or deleterious effect

-Population size affects the relative importance of natural selection versus genetic drift in driving evolutionary change in DNA sequences