module 2

Question 1

define a gene pool

Answer 1

all the alleles present in all individuals in a population or species

Question 2

What is population genetics?

Answer 2

the study of genetic variation in natural populations (interbreeding groups of organisms of the same species living in the same geographical area)

Question 3

What are the two sources of genetic variation?

Answer 3

1. mutation
2. recombination

Question 4

What are somatic vs. germ-line mutations?

Answer 4

1. somatic: occur in the body’s tissues in non-reproductive cells
2. germ-line: occurs in the reproductive cells

Question 5

Why are germ-line mutations more important in evolution than somatic ones?

Answer 5

bcuz germ-line mutations are passed on to the next generation, but somatic effects the invididual

Question 6

Define allele frequency

Answer 6

the proportion of a specified allele among all the alleles of a gene in a population

Question 7

What is fixation?

Answer 7

the process by which one allele replaces all of the other alleles in a population

Question 8

What is genotype frequency?

Answer 8

the proportion of a specified genotype among all the genotypes for a particular gene or set of genes in a population

Question 9

What is considered the “gold standard” for measuring genetic variation?

Answer 9

DNA sequencing

Question 10

What does it mean to say that an allele is “fixed” in a population?

Answer 10

an allele is fixed if there is only one allele for that gene in the population

Question 11

What is evolution?

Answer 11

evolution is a change in allele or genotype frequency over time

Question 12

what is the Hardy-Weinburg equilibrium?

Answer 12

a state in which allele and genotype frequencies do not change over time, implying the absence of evolutionary forces

Question 13

When is a population considered to be in Hardy-Weinberg equilibrium?

Answer 13

1. there is no difference in the survival and reproductive success of individuals with different genotypes
2. the population is sufficiently large to prevent sampling errors
3. populations are not added to or subtracted from by migration
4. there is no mutation
5. individuals mate at random

Question 14

What is non-random mating?

Answer 14

mate selection biased by genotype or relatedness

• occurs when individuals do not mate randomly, individuals might preferentially mate with other AA homozygotes
• affects genotype frequencies from generation to generation, but does not affect allele frequencies

Question 15

Can evolution occur without allele frequency changes?

Answer 15

yes, evolution is change within a population over time in the frequency of alleles OR genotypes

Question 16

What does natural selection result in?

Answer 16

natural selection results in allele frequencies changing from generation to generation according to the allele’s impact on the survival and reproduction of individuals

Question 17

what are adaptations in evolution?

Answer 17

a trait that enhances the fitness of an organism to its environment

results in the organism’s fitness being higher than that of others lacking the trait

the process by which a population becomes progressively better fitted to its environment thru natural selection

Question 18

Define fitness

Answer 18

a measure of the extent to which an individual’s genotype is represented in the next generation

Question 19

What is the modern synthesis theory?

Answer 19

the current theory of evolution, which combines Darwin’s theory of natural selection and Mendelian genetics

Question 20

What is positive. vs negative selection?

Answer 20

1. positive: natural selection that increases the frequency of a favorable allele
2. negative: natural selection that reduces the frequency of a deleterious allele

Question 21

What is balancing selection?

Answer 21

natural selection that acts to maintain two or more alleles of a given gene in a population

Question 22

What are the types of natural selection that act on a population (as a whole)?

Answer 22

1. stabilizing
2. disruptive
3. directional

Question 23

What is stabilizing selection?

Answer 23

a form of selection that selects against extremes and therefore maintains the status quo

*acts in favor of intermediate phenotypes and against extremes

Question 24

What is directional selection?

Answer 24

a form of selection that results in a shift of the mean value of a trait in a population over time

*acts in favor of one extreme and against another

ex. antibiotic resistance

Question 25

What is disruptive selection?

Answer 25

a form of selection that operates in favor of extremes and against intermediate forms, selecting against the mean *acts in favor of extremes and against intermediate phenotypes

Question 26

What are selective pressures?

Answer 26

term to describe the set of environmental conditions, both physical, and biological, that result in some organisms surviving and reproducing more than the others

Question 27

Is artificial selection a form of directional selection?

Answer 27

yes

Question 28

What is artificial selection?

Answer 28

a form of directional selection similar to natural selection, but with selection done intentionally by humans, usually with a specific goal in mind

Question 29

What is sexual selection?

Answer 29

a form of selection that promotes traits that increase an individual's access to reproductive opportunities

Question 30

What is intrasexual selection?

Answer 30

a form of sexual selection involving interactions between individuals of one sex, as when members of one sex compete with one another for access to the other sex

Question 31

What is intersexual selection?

Answer 31

a form of sexual selection involving interaction between males and females, as when females choose from among males

Question 32

What are other forms of evolution besides natural selection?

Answer 32

* nonadaptive mechanisms of evolution -> do not lead to adaptations 1. genetic drift 2. migration 3. mutation 4. non-random mating

Question 33

What is genetic drift?

Answer 33

chance in allele frequency due to chance - can dramatically affect small populations (ie. habitat destruction)

Question 34

What are two forms of genetic drift?

Answer 34

1. bottle neck effect 2. founder event

Question 35

What is the bottleneck effect?

Answer 35

occurs when an originally large population is reduced to just a few individuals *often causes genetic drift

Question 36

What is a founder event?

Answer 36

acute genetic drift that occurs when only a few individuals establish a new population causing allele frequencies to randomly change and loss of genetic variation

Question 37

does migration increase or decrease genetic variation between populations?

Answer 37

migration reduces genetic variation between populations migration causes the homogenization of populations making them more similar to each other and reducing genetic differences between them --> stops speciation from occurring

Question 38

What is migration?

Answer 38

the movement of individuals from one population to another - results in gene flow

Question 39

does mutation increase or decrease genetic variation?

Answer 39

mutations increase genetic variation

Question 40

What effect does nonrandom mating have on genotype frequencies?

Answer 40

non random mating alters genotype frequencies without affecting allele frequencies individuals choose mates according to their genotypes causing certain phenotypes to increase/ decrease

Question 41

Why of all the evolutionary mechanisms is selection the only one that can result in adaptation?

Answer 41

adaptation is the fit between an organism and its environment - only selection causes allele frequencies to change based on how they contribute to the success of an individual in terms of survival and reproduction

Question 42

What is biological evolution?

Answer 42

a change in the frequency of a genetic trait in a population over time

Question 43

When does evolution occur?

Answer 43

evolution occurs when an allele/ genotype becomes more common or less common

Question 44

What are the 5 main mechanisms of evolution?

Answer 44

1. natural selection 2. genetic drift (random) 3. mutation (random) 4. migration/ gene flow (random) 5. nonrandom mating

Question 45

How are new alleles originally formed?

Answer 45

completely new alleles can be formed by mutation (and genetic recombination if there are at least two alleles, happens during meiosis)

Question 46

What mechanisms of evolution can increase genetic variation within a population? it can also lower genetic differentiation between populations?

Answer 46

the mechanism is migration, which causes gene flow.... also reduces genetic differentiation due to homogenization

Question 47

What is genetic drift?

Answer 47

1. random changes in allele frequencies *genetic diversity will stay the same, or decrease

Question 48

What is natural selection?

Answer 48

the process by which traits that increase fitness become more common in a population over generations - only mechanism of evolution that consistently leads to adaptation

Question 49

How do we slow down the effects of natural selection on antibiotics / bacteria?

Answer 49

1. weaken selection pressure: use fewer antibiotics 2. stronger attack: use antibiotics appropriately, overly low doses provide selection even for weakly resistant bacteria 3. multiple selection pressures: produce new and multiple defenses (ie. tuberculosis treatments)

Question 50

The skin color of an individual human is partly determined by MC1R. What is true regarding the MC1R gene?

Answer 50

the MC1R gene is involved with changing the type of melanin produced by skin cells

Question 51

What are random mechanisms of evolution?

Answer 51

1. bottle neck effect 2. sexual genetic recombination 3. genetic drift 4. mutation

Question 52

How might a population gain alleles that are NEW to that group of individuals?

Answer 52

1. genetic recombination 2. gene flow 3. mutations in alleles