Chapter 15

Question 1

coefficient of variation (CV)

Answer 1

the standard deviation of a sample divided by the mean

Question 2

genetic variation

Answer 2

Differences among individuals in a population that are due to differences in genotype.

Question 3

environmental variation

Answer 3

Differences among individuals in a population that are due to differences in the environments they have experienced.

Question 4

genotype-by-environment interaction

Answer 4

Differences in the effect of the environment on the phenotype displayed by different genotypes; for example, among people living in the same location some change their skin color with the seasons and others do not.

Question 5

genome

Answer 5

The corpus of genetic instructions carried by an individual

Question 6

alleles

Answer 6

Variant forms of a gene, or variant nucleotide sequences at a particular locus.

Question 7

genotype

Answer 7

The combination of alleles an individual carries at one or more loci of interest.

Question 8

phenotype

Answer 8

The set of traits an individual exhibits.

Question 9

inducible defense

Answer 9

A character that is adaptive because of its role in evading predation and that develops only in the presence of a cue emanating from the predator.

Question 10

expression

Answer 10

In molecular biology, the production, from the information encoded in a gene, of a functional protein or RNA.

Question 11

epigenetic marks

Answer 11

Chemical modifications of DNA, managed by enzymes encoded in the genome, that can influence phenotype by altering gene expression.

Question 12

reaction norm

Answer 12

The pattern of phenotypic plasticity exhibited by a genotype.

Question 13

phenotypic plasticity

Answer 13

Variation, under environmental influence, in the phenotype associated with a genotype.

Question 14

complementary base pairing

Answer 14

Nucleotides that match up and form hydrogen bonds on opposite strands of a DNA molecule or DNARNA duplex. C complements G; A complements T or U.

Question 15

premutations

Answer 15

Alterations in a DNA sequence, due to chemical degradation and replication errors, that may still potentially be detected and repaired.

Question 16

point mutation

Answer 16

Alteration of a single base in a DNA sequence.

Question 17

transition

Answer 17

In DNA, a mutation that substitutes a purine for a purine or a pyrirnidine for a pyrimidine.

Question 18

transversion

Answer 18

In DNA, a mutation that substitutes a purine for a pyrimidine, or a pyrimidine for a purine.

Question 19

synonymous (or silent) substitution

Answer 19

A DNA substitution that does not
change the amino acid or RNA sequence specified by the gene. Also called a synonymous substitution.

Question 20

nonsynonymous (or replacement) substitution

Answer 20

A DNA substitution that changes the amino acid or RNA sequence specified by a gene. Also called a nonsynonymous substitution.

Question 21

nonsense mutation

Answer 21

A mutation creating a new stop codon in the coding region of a gene.

Question 22

introns

Answer 22

(intervening sequence) A noncoding stretch of DNA nucleotides that occurs between the coding regions of a gene and that must be spliced out after transcription to produce a functional messenger RNA.

Question 23

exons

Answer 23

A nucleotide sequence that occurs between introns and that remains in the messenger RNA after the introns have been spliced out.

Question 24

mean heterozygosity

Answer 24

In a population, either: (1) the average frequency across loci, of heterozygotes; or (2) the fraction of genes that are heterozygous in the genotype of the average individual

Question 25

percentage of polymorphic loci

Answer 25

The fraction of genes in a population that have at least two alleles.

Question 26

allozyme

Answer 26

Distinct forms of an enzyme, encoded by different alleles at the same locus

Question 27

gene duplication

Answer 27

Generation of an extra copy of a locus, usually via unequal crossing-over or retroposition.

Question 28

unequal crossing over

Answer 28

A crossing-over event between mispaired DNA strands that results in the duplication of sequences in some daughter strands and deletions in others.

Question 29

retroposition or retroduplication

Answer 29

The duplication of a genetic sequence resulting from the retrotranscription of a processed mRNA followed by integration into the genome

Question 30

pseudogene

Answer 30

DNA sequences that are homologous to functioning genes, but are not transcribed

Question 31

paralogous

Answer 31

Duplicated genes found in the same genome; describes the relationship among members of the same gene family. A type of genetic homology.

Question 32

orthologous

Answer 32

Genes that diverged after a speciation event; describes the relationship among homologous genes found in different species.

Question 33

Chromosome inversions

Answer 33

A region of DNA that has been flipped, so that the genes are in reverse order; results in lower rates of crossing-over and thus tighter linkage among loci within the inversion.

Question 34

linkage

Answer 34

The tendency for alleles at different loci on a chromosome to be inherited together

Question 35

polymorphic

Answer 35

Describes a population, locus, or trait for which there is more than one phenotype or allele; variable.

Question 36

cline

Answer 36

A systematic change along a geographic transect in the frequency of a genotype or phenotype

Question 37

polyploid

Answer 37

Having more than two haploid sets of chromosomes.

Question 38

common garden experiment

Answer 38

An experiment in which individuals from different populations or treatments are reared together under identical conditions

Question 39

relative fitness

Answer 39

The fitness of an individual, phenotype, or genotype compared with others in the population; can be calculated by dividing the individual’s fitness by either (1) the mean fitness of the individuals in the population, or (2) the highest individual fitness found in the population