Ch 18 Population Genetics

Question 1

genetic rescue

Answer 1

introduction of new genetic variation into an inbred population often dramatically improves the health of the population and can increase its chance of long-term survival

Question 2

Mendilian population

Answer 2

a group of interbreeding, sexually reproducing individuals that have a common set of genes

Question 3

gene pool

Answer 3

common set of genes

Question 4

population genetics

Answer 4

the branch of genetics that studies the genetic makeup of groups of individuals and how a group’s genetic composition changes with time
also the study of evolution

Question 5

genotype frequency

Answer 5

to calculate, add up the number of individuals possessing a genotype and divide by the total number of individuals in the sample (N)
sum of all genotypic frequencies always equal 1

Question 6

allelic frequencies

Answer 6

gene pool of a population can also be described in terms of this
can be calculated from 1) numbers or 2) frequencies of the genotypes

Question 7

Hardy-Weinberg Law

Answer 7

a mathematical model that evaluates the effect of reproduction on the genotypic and allelic frequencies of a population
Assumptions: if a population is large, randomly mating, and not affected by mutation, migration or natural selection, then
Prediction 1: the allelic frequencies of a population do not change; and
Prediction 2: the genotypic frequencies stabilize after one generation in the proportions p^2, 2pq, and q^2 where p equals the frequency of allele A and q equals the frequency of allele a

Question 8

Hardy-Weinberg equilibrium

Answer 8

when genotypes are in the expected proportions of p^2, 2pq, and q^2, the population is said to be in this

Question 9

inbreeding

Answer 9

one form of nonrandom mating which is preferential mating between related individuals
leads to an increase in the proportion of homozygotes and a decrease in the proportion of heterozygotes in a population

Question 10

processes that bring about change in allelic frequencies

Answer 10

mutation, migration, genetic drift (random effects due to small population size) and natural selection

Question 11

equilibrium

Answer 11

a point at which there is no change in the allelic frequencies of a population

Question 12

migration or gene flow

Answer 12

the influx of genes from other populations
overall effect: 1) it prevents populations from becoming genetically different from one another and 2) it increases genetic variation within populations

Question 13

sampling error

Answer 13

deviation from an expected ratio due to limited sample size

arises when gametes unite to produce progeny

Question 14

genetic drift

Answer 14

changes in allelic frequencies

Question 15

effective population size (Ne)

Answer 15

population geneticists define population size as the equivalent number of breeding adults

Question 16

founder effect

Answer 16

occurs when a population is established by a small number of individuals

Question 17

genetic bottleneck

Answer 17

develops when a population undergoes a drastic reduction in size

Question 18

fixation

Answer 18

when an allele has reached a frequency of 1, it has reached this
leads to a loss of genetic variation within a population

Question 19

fitness

Answer 19

the reproductive success of a genotype compared with that of other genotypes in a population

Question 20

selection coefficient (s)

Answer 20

the relative intensity of selection against a genotype

Question 21

directional selection

Answer 21

one allele or trait is favored over another
Type 2 of natural selection is this
WAA=WAa < WAA

Question 22

overdominance

Answer 22

also called heterozygote advantage
both alleles are favored in the heterozygote and neither allele is eliminated from the population
Type 5 of natural selection is this
WAA < WAa > Waa

Question 23

underdominance

Answer 23

the heterozygote has lower fitness than either homozygote
leads to an unstable equilibrium
Type 6 of natural selection is this
WAA > WAa < Waa

Question 24

evolution

Answer 24

genetic change taking place in a group of organisms

two step process: genetic variation arises and change in the frequencies of genetic variants