Lecture 7 & 8: Selection

Question 1

What is the significance of the Hardy-Weinberg assumptions?

Answer 1

If none of the assumptions are broken, no evolutionary forces, no change in allele frequencies.

Question 2

Define fecunfity

Answer 2

the actual reproductive rate of an organism or population

Question 3

What does fitness include?

Answer 3

Fitness = genotype-specific survivorship and fecundity, how good are you at getting your genes into the next generation

Question 4

Define selection coefficient

Answer 4

measure of the relative fitness of a population, , s = (1-fitness), force operating against a genotype

Question 5

Define average fitness

Answer 5

w bar, weighted fitness of all individuals, fitness of each genotype x frequency of each genotype

Question 6

What does the response to selection depend on?

Answer 6

The response to selection depends on the strength of selection

Question 7

What does the strength of selection depend on?

Answer 7

The strength of selection depends on the difference in fitness values (between on another), greater difference = greater strength

Question 8

What is the relationship between selection and genetic variation.

Answer 8

The rate of natural selection is proportional to the genetic variation in the population

Question 9

Define “marginal” overdominance

Answer 9

The average (marginal) fitness for the heterozygotes is higher that for either homozygote (with multiple niches)

Question 10

What is directional selection?

Answer 10

Mode of selection in which an extreme phenotype if favored over other phenotypes causing the allele frequency to shift

Question 11

What is balancing selection?

Answer 11

Refers to a number of selective processes by which multiple alleles are maintained in the gene pool of a population at frequencies above that of gene mutations.

Question 12

What is frequency dependent selection?

Answer 12

Evolutionary process where the fitness of a phenotype depends on its frequency relative to other phenotypes in a given population.

Question 13

Define selective sweep

Answer 13

The reduction or elimination of variation among the nucleotides in neighboring DNA of a mutation as a result of recent and strong positive selection

Question 14

Define hitchhiking

Answer 14

is the change in the frequency of an allele that is caused by linkage to a positively or negatively selected allele at another locus.