Ch.27: Population Genetics

Question 1

Describe polymorphism

Answer 1

the observation that many traits display variation within a population and can describe a gene that commonly exists as 2 or more alleles in a population; occurs when two or more alleles influence a phenotype

Question 2

What are the two fundamental calculations for population genetics?

Answer 2

-The allele frequency formula allows us to calculate the frequency of alleles in a population

-The genotype frequency formula allows us to calculate the frequency of genotypes in a population

Question 3

What is the allele and genotype frequencies for a given trait?

Answer 3

always less than or equal to 1

Question 4

What is the allele and genotype frequencies for polymorphic genes?

Answer 4

frequencies of all of the alleles should add up to 1.0

Question 5

What does the Punnett Square analysis give?

Answer 5

the same result mathematically
as the Hardy Weinberg equation p2 + 2pq + q2 = 1

Question 6

What are 4 mechanism that alter existing genetic variation?

Answer 6

-Natural Selection
-Random genetic drift
-Migration
-Nonrandom mating

Question 7

What is Darwinian (relative) fitness?

Answer 7

a quantitative assessment of the relative likelihood that a genotype
will survive and contribute to the gene pool of the next generation; the values (w) is a measure of reproductive superiority
and it should not be confused with physical fitness

Question 8

What are the 4 ways that
natural selection may operate?

Answer 8

-Directional selection
-Balancing
-Disruptive or diversifying selection
-Stabilizing selection

Question 9

Describe directional selection

Answer 9

favors individuals at one extreme of a phenotypic distribution
that are more likely to survive and reproduce in a particular environment

Question 10

What does directional selection affect?

Answer 10

the Hardy-Weinberg equilibrium and allele frequencies by favoring the extreme phenotype as determined by w, the relative fitness value

Question 11

What does the mean fitness of the population, (wU), formula allows us to calculate?

Answer 11

changes in the allele frequencies, genotype frequencies

Question 12

What are the 2 types of balanced polymorhpisms?

Answer 12

-Heterozygote advantage: the heterozygote has a higher fitness than either homozygote

-Negative frequency-dependent selection: the fitness level of a genotype decreases when its frequency becomes higher- rare individuals have a higher fitness level than the more common individuals and are more likely to reproduce

Question 13

What is the selection coefficient used for?

Answer 13

to determine the allele
frequencies of populations with polymorphisms when the
polymorphisms reach equilibrium

Question 14

What do disruptive/diversifying selection favor?

Answer 14

the survival of two or more different genotypes with different phenotypes

Question 15

What happens in a stabilizing selection?

Answer 15

the extreme phenotypes are selected against

Question 16

Describe genetic drift

Answer 16

-refers to random changes in allele frequencies due to random fluctuations
-In a large population, N = 1000, it takes longer for genetic drift to occur than in a small population, N = 20
-In small populations, N = 20, an allele can become fixed
or be lost very quickly

Question 17

What can genetic drift be impacted by? What happens if fixation occurs?

Answer 17

-either the bottleneck effect or the founder effect

-how many generations is it likely to take depends on the number of
individuals in the population

Question 18

What is the bottleneck effect?

Answer 18

In nature, a population can be reduced dramatically in size by a natural disaster that eliminates
individuals regardless of their genotype

Question 19

What is the founder effect?

Answer 19

A small group of individuals separates from a larger
population and establishes itself in a new location

Question 20

What is the coefficient of inbreeding is also called?

Answer 20

fixation coefficient, F;
Health studies have shown that a F of less than 5% is desire

Question 21

New mutations may be..?

Answer 21

-Beneficial
-Neutral
-Deleterious
-Neutral and deleterious mutations are far likelier to occur than beneficial mutation

Question 22

What are important notes about repetitive sequences?

Answer 22

-they differ from person to person and can be used diagnostically in DNA fingerprinting
-matches between the child and the mother and father should be different
-the % matches between the mother or father and the child should be around 50%

Question 23

What can you do with DNA from a crime scene?

Answer 23

amplify, probe, and run on a gel to identify a suspect