Definitions

Question 1

Homologs

Answer 1

Traits or sequences that are similar in disparate groups because of common ancestry

Question 2

Synonymous

Answer 2

A change in the protein coding region of a gene that does not change the amino acid encoded

Question 3

Nonsynonymous

Answer 3

A change in the protein coding region of a gene that alters the amino acid encoded

Question 4

Derived

Answer 4

An allele that arises via a novel mutation and does not achieve fixation in a population (as contrasted with an ancestral allele)

Question 5

Genetic drift

Answer 5

Change in allele frequencies over time due to chance (e.g. random sampling)

Question 6

Linkage disequilibrium (LD)

Answer 6

Tendency of certain variants on the same chromosome to be coinherited at above chance rates within a population (e.g., owing to selection or founder effects)

Question 7

Ancestral

Answer 7

An allele that was pre-existing in a population and from which a derived allele may arise

Question 8

Single nucleotide polymorphism (SNP)

Answer 8

Individual base-pair sites in the genome of an organism where multiple variants exist

Question 9

Codon usage bias

Answer 9

The tendency of an organism’s genome to more commonly have a certain codon for a given amino acid than any of its synonymous counterparts

Question 10

Unfolded site frequency spectrum

Answer 10

Spectrum of allele frequencies that takes into account only derived and not ancestral alleles

Question 11

Copy number variants (CNVs)

Answer 11

A form of structural variant in which multiple copies of a genetic region exist

Question 12

Microsatellites

Answer 12

Genetic regions that consist of repeating sequences of two to six base pairs. Also referred to as short tandem repeats (STRs) or simple sequence repeats (SSRs)

Question 13

Structual variants (SVs)

Answer 13

Alterations in the genome that affect relatively large chromosomal regions, including deletions and insertions (indels), translocations, inversions, and duplications

Question 14

Pleiotropy

Answer 14

A trend in which one genotype affects multiple phenotypes

Question 15

Heterozygous advantage

Answer 15

A trend in which the fitness of a heterozygote is greater than that of either homozygote. Also referred to as overdominance

Question 16

Frequency dependent selection

Answer 16

A trend in which the fitness of a given genotype is correlated with its prevalence in the population (e.g., if an allele is advantageous when it is rare)

Question 17

Codominance

Answer 17

Condition in which multiple alleles are dominant; the heterozygote expresses phenotypes associated with both alleles