Ch09-

Question 1

The evolution of resistance may incur a cost. Is resistance evolution reversible if antibiotics are not being used?

Answer 1

yes, but not always

Question 2

Why do bacteria with resistance to antibiotics still survive although antibiotics are not in use or lessened?

Answer 2

they gain an allele that compensate the cost of resistant that arised from a compensatory mutation

Question 3

define additive genetic effects

Answer 3

when a phenotype of a individual is determined by the sum of the effects of each alleles it has

Question 4

define latent variation

Answer 4

possible genotypes/phenotypes among a large variation that are not represented in a population

Question 5

why is latent variation important?

Answer 5

in the absent of mutation, new phenotypes can still arise from latent variation by selection & genetic reassortment

Question 6

define epistasis

Answer 6

when two loci influence a character by influencing each other

Question 7

define haplotypes

Answer 7

a set of alleles, one at each locus under consideration

Question 8

why do we need to keep tract of the alleles and haplotypes frequencies to treat the population genetics of multiple loci

Answer 8

because allele frequencies are not solely responsible for haplotype frequencies, linkage is too

Question 9

define Linkage disequilibrium

Answer 9

A statistical bias in the association of alleles corresponding to different loci

Question 10

what can produce Linkage disequilibrium?

Answer 10

from a mutation, natural selection only when the loci are epistasis, migration, & genetic drift

Question 11

when a linkage disequilibrium is present in a population, what happens to it in the absence of other evolutionary processes?

Answer 11

it dissipates by recombination

Question 12

how can new haplotypes be generated?

Answer 12

by the recombination of two heterozygotes

Question 13

what happens when 4 haplotypes exist in a population & recombination is absent?

Answer 13

• no haplotypes are produced

- genotype & linkage disequilibrium is unchanged

Question 14

what happens when 4 haplotypes exist in a population & recombination is present?

Answer 14

• haplotypes are produced, decreasing frequency of previous existing haplotype
• coupling heterozygotes decreases as new genotypes appears

Question 15

what are the consequences of genetic linkage?

Answer 15

genetic hitchhiking & background selection

Question 16

in what case is genetic hitchhiking not harmful?

Answer 16

periodic selection in haploid organism

Question 17

ultimately how do bacterial resistance to antibiotics that have been withdrawn from general use still persist?

Answer 17

due to periodic selection. since bacterial genome acts as a single haplotype, each new arising beneficial mutations are sweep into fixation carrying all other alleles