Pages 478-482; 483-486

Question 1

sampling error

Answer 1

occurs when the allele frequencies of a chosen subset of a population (the sample) are different from those in the total population, by chance.

Question 2

drift occurs

Answer 2

in every population, in every generation, but especially in small populations.

Question 3

Alleles containing silent mutations, usually in the third position of a codon, do not change the gene product. As a result

Answer 3

most of these alleles have little or no effect on the phenotype. Yet these alleles routinely drift to high frequency or fixation over time.

Question 4

Three important points about genetic drift:

Answer 4

• Genetic drift is random with respect to fitness. The changes in allele frequency that it produces are not adaptive.
• Genetic drift is most pronounced in small populations.
• Over time, genetic drift can lead to the random loss or fixation of alleles. When this occurs, genetic variation in the population declines.

Question 5

genetic marker

Answer 5

specific allele that causes a distinctive phenotype.

Question 6

genetic drift

Answer 6

decreases genetic variation within populations and increased genetic differences between populations.

Question 7

founder event

Answer 7

when a group of individuals immigrates to a new geographic area and establishes a new population. If the new population is small enough, the allele frequencies in the new population are almost guaranteed to be different from those in the source population – due to sampling error.

Question 8

founder effect

Answer 8

a change in allele frequencies that occurs when a new population is established.

Question 9

population bottleneck

Answer 9

when a large population experiences a sudden reduction in size.

Question 10

genetic bottleneck

Answer 10

follow population bottlenecks; sudden reduction in the number of alleles in a population. Genetic drift occurs during genetic bottlenecks and causes a change in allele frequency.

Question 11

point mutation

Answer 11

if a change in nucleotide sequence occurs in a stretch of DNA that cods for a protein, the new allele may result in a polypeptide with a novel amino acid sequence. If the mutation occurs in a stretch of DNA that codes for regulatory RNA, the new allele may result in a change in regulation of the expression of other alleles.

Question 12

chromosome-level mutations

Answer 12

one consequence is gene duplication, which increases the number of copies of a gene. If duplicated genes diversify via point mutations, they can lose their function or create new alleles.

Question 13

Lateral gene transfer (horizontal gene transfer)

Answer 13

transfer of genes from one species to another, rather than from parent to offspring, might be a more important source of genetic variation than previously realized.

Question 14

Most mutations in sequences that code for a functional protein or RNA result in

Answer 14

deleterious alleles, which lowers fitness.

Question 15

deleterious alleles

Answer 15

tend to be eliminated via purifying selection.

Question 16

beneficial allele

Answer 16

an allele that allows individuals to produce more offspring. Mutation that occurs in sequences that code for a functional protein or RNA.

Question 17

Mutation in eukaryotes rarely causes a change

Answer 17

from the genotype frequencies expected under the Hardy-Weinberg principle.