Lesson 8: Natural Selection

Question 1

What are the four evolutionary mechanisms

Answer 1

1. genetic drift
2. migration
3. mutation
4. natural selection

Question 2

types of mechanisms

Answer 2

1. non-adaptive mechanism
2. adaptive mechanism

Question 3

what are the non-adaptive mechanisms

Answer 3

1. genetic drift
2. migration
3. mutation

Question 4

what are the adaptive mechanisms

Answer 4

natural selection

Question 5

According to Darwin, evolution acts through changes in what?

Answer 5

allelic frequency at each generation

Question 6

According to Darwin, how does evolution happen

Answer 6

via natural selection

Question 7

where does natural selection act upon

Answer 7

genetic or epigenetic variation in population

Question 8

generates genetic variation

Answer 8

mutation

Question 9

changes expression of genes

Answer 9

epigenetic modification

Question 10

can reduce genetic variation

Answer 10

genetic drift

Question 11

Darwin’s contribution: Population speciation as result of natural selection

Answer 11

1. too many offpsring produced
2. limited resources and competition
3. variation in population
4. better adapted individuals survive
5. survivors leave more offspring
6. average character of population is altered

Question 12

natural selection is not random, but __

Answer 12

deterministic

Question 13

Selection imposed by transmittion rate on virulence of HIV

Answer 13

1. high transmission rate: high virulence
2. low transmission rate: low virulence

Question 14

can grow fast and jump to the next host; ok if host dies; genetic strain that grows faster will win

Answer 14

high transmission rate: high virulence

Question 15

more virulent strains would die with the host and get selected out; less virulent strain will win

Answer 15

low transmission rate: low virulence

Question 16

mutant allele of the receptor CCR5

Answer 16

CCR5-Δ32

Question 17

traits that are usually coded by one or a few genes (loci)

Answer 17

discrete traits

Question 18

trait coded by many loci

Answer 18

quantitative traits

Question 19

Different modes of selection

Answer 19

1. Directional selection
2. Stabilizing selection
3. Disruptive selection

Question 20

selection changes frequency of allelese in one direction

Answer 20

directional selection

Question 21

• selection acts against the extremes (favors intermediate trait)
• purifying selection
• average trait value stays the same
• genetic diversity is reduced

Answer 21

stabilizing selection

Question 22

• selection favors the extremes
• genetic diversity is increased (help maintain genetic variation; knowck our alleles that code for intermediate traits)
• can lead to formation of new species

Answer 22

disruptive selection

Question 23

disruptive selection can lead to what?

Answer 23

formation of new species

Question 24

example of disruptive selection

Answer 24

sexual selection for different traits (blue birds mate with blue, red birds mate with red)

Question 25

generic term to refer to any type of selection that acts to maintain genetic variation in a population

Answer 25

balancing selection

Question 26

Examples of balancing selection

Answer 26

1. selection for heterozygotes 2. selection for different traits in different environments 3. selection for different traits at different times

Question 27

selection for different traits at different times

Answer 27

fluctuating selection

Question 28

Selection: With malaria

Answer 28

balancing selection for heterozygote

Question 29

lead to amino acid change

Answer 29

nonsynonymous mutation/missense mutation (position 1 and 2)

Question 29

Selection: Without malaria

Answer 29

directional selection for homozygous wild type (HAHA)

Question 30

does not lead to amino acid change

Answer 30

synonymous mutation/silent mutation (position 3)

Question 31

test for selection

Answer 31

Ka/Ks test

Question 32

Ka

Answer 32

nonsynonymous substitution rate

Question 33

Ks

Answer 33

synonymous substitution rate

Question 34

absence of selection

Answer 34

Ka/Ks = 1

Question 35

positive selection

Answer 35

Ka/Ks > 1

Question 36

negative selection / purifying selection

Answer 36

Ka/Ks < 1

Question 37

out of all possible number of mutations, how many fixed

Answer 37

substitution rate

Question 38

selection occurs through __ __ which is not random

Answer 38

differential reproduction

Question 39

Selection favoring the heterozygote

Answer 39

Overdominance