Chapter 18: Population and Evolutionary Genetics

Question 1

Define mendelian population

Answer 1

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

Question 2

Define gene pool

Answer 2

A common set of genes withing a group

Question 3

Define genotype frequency

Answer 3

the number of individuals with a given genotype divided by the total number of individuals

Question 4

Define allelic frequencies

Answer 4

The gene pool of a population

Question 5

Define Hardy-Weinberg Law

Answer 5

A mathematical model that evaluates the effect of reproduction on the genotypic and allelic frequencies of a population

Question 6

What are the six factors in population genetics?

Answer 6

1. Mating patterns
2. Migration
3. Mutation
4. Recombination
5. Natural selection
6. Random fluctuation

Question 7

What are the 5 assumptions of Hardy-Weinberg?

Answer 7

1. Mating is random
2. Population is large
3. There is no selection
4. No mutation
5. No migration

Question 8

Define genetic drift

Answer 8

Changes in allele frequency due to random factors

Question 9

Does genetic drift affect large populations or small population more?

Answer 9

Small

Question 10

Natural selection has three categories regarding genetics; what are they?

Answer 10

1. Directional selection
2. Overdominance
3. Underdominance

Question 11

Define directional selection

Answer 11

One allele has higher fitness than the other

Question 12

Define overdominance

Answer 12

Heterozygotes have higher fitness than either homozygotes

Question 13

Define under dominance

Answer 13

Heterozygotes have lower fitness than either homozygote

Question 14

What is the difference between relative fitness vs. absolute fitness?

Answer 14

Relative: relative to other genotypes
Absolute: measures contribution to next generation

Question 15

Which type of fitness is most commonly measured?

Answer 15

Relative fitness

Question 16

How do mutations allow scientists to predict evolutionary patterns?

Answer 16

Mutation occurs at a consistent rate, changes in DNA can be observed to allow dating of changes and how long ago they occurred

Question 17

How do you calculate the frequency of an allele?

Answer 17

Frequency of an allele = (number of copies of the allele) / (number of copies of all alleles at the locus)

Question 18

If the requirements of the Hardy-Weinberg law are met, what are the two predictions?

Answer 18

1. The allelic frequencies of a population do not change

AND

2. The genotypic frequencies stabilize (will not change) after one generation in the proportions p^2 (the frequency of AA), 2pq (the frequency of Aa), and q^2 (the frequency of aa), where p equals the frequency of “A” and q equals the frequency of allele “a”.

Question 19

Define Hardy-Weinberg equilibrium

Answer 19

When genotypes are in the expected proportions of p^2, 2pq, and q^2

Question 20

(1) Which of the following statements is NOT an assumption of the Hardy-Weinberg law?

a. The allelic frequencies (p and q) are equal
b. The population is randomly mating
c. The population is large
d. Natural selection has no effect

Question 21

(2) In cats, all-white color is dominant over colors other than all-white. In a population of 100 cats, 19 are all-white. Assuming that the population is in Hardy-Weinberg equilibrium, what is the frequency of the all-white allele in this population?

Question 22

Define inbreeding

Answer 22

A form of non-random mating when organisms have a preferential mating between related individuals.

Question 23

Define inbreeding depression

Answer 23

An increase appearance of lethal and deleterious traits caused from inbreeding

Question 24

Nonrandom mating alters the frequencies of _____ but not the frequencies of _____

a. alleles, phenotypes
b. genotypes, alleles
c. phenotypes, genotypes
d. alleles, genotypes

Answer 24

b. genotypes, alleles

Nonrandom mating alters the frequencies of genotypes but not the frequencies of alleles

Question 25

Define equilibrium

Answer 25

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

Question 26

Recurrent _____ cause(s) changes in the frequencies of alleles. a. inbreeding b. competition c. mutations d. cell division

Answer 26

c. mutations Recurrent mutations cause changes in the frequencies of alleles.

Question 27

At equilibrium, how are allelic frequencies determined?

Answer 27

By forward and reverse mutation rates. Ex: If mutation rates are low, the effect of mutation on allelic frequencies per generation is very small

Question 28

Define migration / gene flow

Answer 28

An influx of genes from other populations

Question 29

Migration has two major effects. What are they?

Answer 29

1. Causes the gene pools of different populations to become more similar 2. Adds genetic variation to populations

Question 30

(3) In each generation, 10 random individuals migrate from population A to population B. What will happen to allelic frequency q as a result of migration when q is equal in populations A and B? a. q in A will decrease b. q in B will increase c. q will not change in either A or B d. q in B will become q^2

Question 31

Define sampling error

Answer 31

A deviation from an expected ratio due to limited sample size

Question 32

Define effective population size (Ne)

Answer 32

When population size is the equivalent number of breeding adults

Question 33

(4) Which of the following statements describes an example of genetic drift? a. Allele g for fat production increases in a small population because birds with more body fat have higher survivorship in a harsh winter b. Random mutation increases the frequency of allele A in one population but not in another c. Allele R reaches a frequency of 1.0 because individuals with genotype rr are sterile d. Allele m is lost when a virus kills all but a few birds in a population and, just by chance, none of the surviving birds possess allele m

Question 34

Define founder effect

Answer 34

A way that sampling errors can arise from the establishment of a population by a small number of individuals

Question 35

Define genetic bottleneck

Answer 35

A way in which genetic drift arises is when a population undergoes a drastic reduction in size

Question 36

Define fixation

Answer 36

When an allele has reached a frequency of 1 Explanation: Through random change, an allele may eventually reach a frequency of either 1 or 0, at which point all individuals in the population are homozygous for one allele. 0 means an allele becomes lost in a population, and 1 means the allele is "fixed" in the population

Question 37

When an allele reaches a frequency of 0 in a population, it is impossible to get that allele back. a. True b. False

Answer 37

b. False The allele can return to the population through migration of another population or by mutation

Question 38

What are the 3 causes of genetic drift?

Answer 38

1. Continuous small population size 2. Founder effect 3. Genetic bottleneck

Question 39

Define fitness

Answer 39

The relative reproductive success of a genotype

Question 40

Define selection coefficient (s)

Answer 40

The relative intensity of selection against a genotype

Question 41

How is natural selection measured?

Answer 41

Natural selection is measured as fitness

Question 42

(5) The average numbers of offspring produced by three genotypes are GG = 6, Gg = 3, and gg = 2. What is the fitness of Gg? a. 3 b. 0.5 c. 0.3 d. 0.27

Question 43

Define evolution

Answer 43

In the biological sense, refers only to genetic change taking place in a group of organisms

Question 44

Define anagenesis

Answer 44

Evolution taking place in a single lineage (a group of organisms connect by ancestry) over time

Question 45

Define cladogenesis

Answer 45

The splitting of one lineage into 2 and the two branches no longer have a common gene pool and evolve independently of one another

Question 46

Define species

Answer 46

Different kinds or types of living organisms

Question 47

Define the biological species concept.

Answer 47

The method used to separate organisms into independently evolving units

Question 48

Define the reproductive isolating mechanism.

Answer 48

Any biological factor or mechanism that prevents gene exchange

Question 49

Define prezygotic reproductive isolating mechanisms.

Answer 49

The prevention of gametes from two different species fusing together and forming a hybrid zygote

Question 50

Define postzygotic reproductive isolating mechanisms.

Answer 50

The gametes of two species may fuse and form a zygote, but there is no gene flow between the two species, either because other resulting hybrids are inviable or sterile or because reproduction breaks down in subsequent generations