Chapter 27

Question 1

What is population genetics?

Answer 1

extent of genetic variation within a group of individuals and changes in that variation over time (focus shifted away from individual and toward population of which the individual is a member)

Question 2

What is the gene pool?

Answer 2

All alleles of every gene in a population (only individuals that reproduce contribute to gene pool of next generation)

Question 3

What is the goal of population geneticists?

Answer 3

Make predictions about how generations change due to genetic variation within the gene pool

Question 4

What is a population?

Answer 4

group of individuals of the same species that occupy the same region and can interbreed with each other

Question 5

What are local populations?

Answer 5

smaller groups within a population, often separated by moderate geographic barriers (ex: deer in ohio different from deer in new massachusetts)

Question 6

What are three ways a population may change?

Answer 6

size, geographic location, genetic composition

Question 7

What is polymorphism?

Answer 7

refers to observation that many traits display variation within a population (ex: Hawaiin happy-face spider that differ in alleles that affect color and pattern)

Question 8

How can a gene be described that commonly exists as 2 or more alleles in a population?

Answer 8

Polymorphic
(monomorphic gene exists predominantly as a single allele)

Question 9

What is a single-nucleotide polymorphism (SNP)?

Answer 9

A change in single base pair in DNA, SNPs account for 90% of variation among people, may not lead to change in phenotype

Question 10

What is an example of SNP?

Answer 10

Sickle cell disease caused by a deletion that eliminates function

Question 11

What is the equation for allele frequency?

Answer 11

Allele Frequency = (Number of copies of an allele in a population) / (Total number of alleles for that gene in a population)

Question 12

What is the equation for genotype frequency?

Answer 12

Genotype frequency = (Number of individuals with a particular genotype in a population) / (Total number of individuals in a population)

Question 13

Are polymorphisms common or rare in natural populations?

Answer 13

very common

Question 14

What is the Hardy-Weinberg equation?

Answer 14

simple mathematical expression that relates allele and genotype frequencies in a population, also called an equilibrium (no evolution/change)
p^2 + 2pq + q^2 = 1
(p is dominant and q is recessive)

Question 15

A gene exists in two alleles designated D and d. If 48 copies of this gene are the D allele and 152 are the d allele, what is the allele frequency of D?

Answer 15

0.24

Question 16

The allele frequency of C is 0.4 and that of c is 0.6. If the population is in Hardy-Weinberg equilibrium, what is the frequency of heterozygotes?

Answer 16

0.48

Question 17

Which of the following is a factor that, by itself, does not promote widespread changes in allele or genotype frequencies?
a. new mutation
b. natural selection
c. genetic drift
d. migration
e. nonrandom mating

Answer 17

a. new mutation

Question 18

What are the five conditions required to reach equilibrium?

Answer 18

no new mutations, no genetic drift (no change of frequencies due to chance alone), no migration, no natural selection, random mating

Question 19

What is the null hypothesis in HW equilibrium?

Answer 19

No change/evolution

Question 20

If null hypothesis is not rejected, you can accept the hypothesis that the population is __________.

Answer 20

in equilibrium

Question 21

If the null hypothesis is rejected, the population is __________.

Answer 21

in disequilibrium

Question 22

What is microevolution?

Answer 22

describes changes in a population’s gene pool from generation to generation, driven by: mutation, random genetic drift, migration, natural selection, nonrandom mating (everything opposite HW)

Question 23

In the theory of natural selection, phenotypes may vary with regard to their _____________.

Answer 23

reproductive success

Question 24

What is fitness?

Answer 24

Measure of reproductive success in relative fitness values (ω), relative likelihood that a genotype will survive and contribute to gene pool of next generation

Question 25

For calculating fitness values, the gene with the highest reproductive ability (most offspring) is given a fitness value of _____.

Answer 25

1.0

Question 26

Does natural selection act on genotypes or phenotypes?

Answer 26

Phenotypes

Question 27

Directional selection

Answer 27

Favors survival of one extreme phenotype that is better adapted to an environmental condition (choosing one phenotype as more fit)

Question 28

Balancing selection

Answer 28

Favors maintenance of two or more alleles (heterozygote advantage)

Question 29

Disruptive (or diversifying) selection & example

Answer 29

Favors survival of two (or more) different phenotypes Caused by fitness values for a given genotype that vary in different environments Example: snail that lives in woods (brown color favored on soil, pink shell favored on leaf litter) and open fields (yellow color favored)

Question 30

Stabilizing selection & example

Answer 30

Favors survival of individuals with intermediate phenotypes Tends to decrease genetic diversity Example: laying eggs

Question 31

Mean fitness of the population & equation

Answer 31

Measure of how fit the whole population is p^2wAA + 2pqwAa + q^2waa = w (with bar on top) Divide both sides by mean fitness and the equation will be set equal to 1 (slide 29)

Question 32

Natural selection raises the _________ of the population from one generation to the next.

Answer 32

mean fitness

Question 33

What is the selection coefficient equation

Answer 33

measures the degree to which a genotype is selected against s = 1 - w w is fitness

Question 34

What is negative frequency-dependent selection?

Answer 34

type of balancing selection, rare individuals have a higher fitness than more common individuals; more likely to reproduce, selection always favors less numerous genotype

Question 35

Name and example of frequency-dependent selection

Answer 35

Rewardless flower - relative fitness of the less-common flower increases

Question 36

Genetic drift

Answer 36

random changes in allele frequencies due to random fluctuations, just chance based Favors either loss or fixation of an allele Less effect on large populations, rate depends on population size

Question 37

Expected number of new mutations (genetic drift) equation

Answer 37

Expected number of new mutations = 2Nu (if each individual has two copies of the gene of interest) u = mutation rate N = number of individuals in population New mutation more likely to occur in large populations

Question 38

Probability of fixation of a newly arising allele due to genetic drift =

Answer 38

1/2N

Question 39

What are the effects on mutations and fixations due to value of N in genetic drift?

Answer 39

Large N: new mutation more likely but has greater chance of being eliminated due to random genetic drift Small N: new mutations less likely but has greater chance of being fixed in pop.

Question 40

Equation for number of generations it takes for fixation

Answer 40

t (with line on top) = 4N N is number of individuals in population assuming that males and females equally contribute

Question 41

Bottleneck effect

Answer 41

Natural disaster randomly eliminates individuals regardless of phenotype

Question 42

Founder effect

Answer 42

Small group of individuals separates from larger population and establishes colony in new location 2 important consequences: founding population is expected to have less genetic variation than original pop., founding pop. will have allelic frequencies that may differ markedly from original pop. as matter of chance

Question 43

Gene flow

Answer 43

Transfer of alleles from donor pop. to recipient pop., changing its gene pool Recipient pop. called conglomerate

Question 44

Equation for calculating change in allele frequency in conglomerate pop.

Answer 44

delta pc = m(pD - pR) delta pc: change in allele frequency in conglomerate population pD: allele frequency in donor pop. pR: allele frequency in original recipient pop. m: proportion of migrants in conglomerate pop. m=(number of migrants in conglomerate pop.)/(total number of individuals in conglomerate population) pc = pR +delta pc

Question 45

Bidirectional migration

Answer 45

Tends to reduce allele frequency differences between populations and can enhance genetic diversity within population

Question 46

Assortative mating (positive and negative)

Answer 46

Individuals don't mate randomly Positive - more likely to mate due to similar phenotypic characteristics Negative - individuals with dissimilar phenotypes mate preferentially

Question 47

Inbreeding

Answer 47

mating between genetically-related individuals, decreases overall diversity, gene pool smaller

Question 48

Outbreeding

Answer 48

mating between genetically unrelated individuals

Question 49

Inbreeding/fixation coefficient (F)

Answer 49

Degree of relatedness in pedigree, probability that gene in inbred individual is homozygous due to its inheritance from common ancestor F = sum of ((1/2)^n (1+FA)) n: number of individuals in inbreeding path (excluding inbred offspring) FA: breeding coefficient of common ancestor

Question 50

Inbreeding example, frequencies of A and a are p and q

Answer 50

p^2 + fpq = frequency of AA 2pq(1-f) = frequency of Aa q^2 + fpq = frequency of aa

Question 51

Inbreeding depression

Answer 51

Inbreeding in natural populations will lower overall fitness

Question 52

Ways to change genetic variation

Answer 52

syke slide 75 has massive chart

Question 53

Out of beneficial, neutral, and deleterious mutations, which is most likely?

Answer 53

Neutral and deleterious far likelier

Question 54

Mutation rate

Answer 54

probability that a gene will be altered by new mutation delta q = up u: mutation rate of an allele into a different allele q: allele frequency of new allele p: allele frequency of current allele

Question 55

To calculate the change in allele frequency after any number of generations:

Answer 55

(1-u)^t = pt/p0 u: the mutation rate of the conversion of original allele to new allele t: the number of generations p0: the frequency of original allele in the starting generation pt: the frequency of allele original allele after t generations

Question 56

Mutations are important fro evolution but has ______ impact in changes of allele frequency.

Answer 56

negligible

Question 57

check slide 49