Week 10

Question 1

define: phenotypic frequency

Answer 1

the proportion of individuals in a population that are of a particular phenotype

Question 2

define: genotype frequency

Answer 2

the proportion of individuals in a population that are of a particular genotype

Question 3

define: allele frequency

Answer 3

the proportion of all copies of a gene in a population that are of a given allele type

Question 4

what 5 assumptions does the Hardy-Weinberg Law depend on

Answer 4

1) the population includes a very large, number of individuals that all have equal access to mating
2) the individuals mate at random
3) no new mutations appear
4) there is no migration into or out of the population
5) no natural selection

Question 5

what can you accurately calculate when a population is at Hardy-Weinberg equilibrium

Answer 5

• allele frequency
• genotype frequency
• phenotype frequency

Question 6

what is the Hardy-Weinberg equation (looking at 2 genes)

Answer 6

p² + 2pq + q² = 1

Question 7

after how many generations do allele frequency for particular gene remain stable at Hardy-Weinberg equilibrium

Answer 7

one

Question 8

how do you compute genotype frequency

Answer 8

individual possessing the genotype ÷ number of individuals in the sample

Question 9

how do you compute phenotype frequency

Answer 9

individual possessing the phenotype ÷ number of individuals in the sample

Question 10

how do you compute allele frequency

Answer 10

(2 x # of homozygous individuals with that allele + # of heterozygous individuals) ÷ (2 x number of individuals in the sample)

Question 11

how can you check if variation of H-W law expected numbers and expected numbers is significant

Answer 11

perform a chi-square analysis

Question 12

do allele frequencies change for generation to generation when in H-W equilibrium

Answer 12

no, they do not

Question 13

define: genetic drift

Answer 13

unpredictable, chance fluctuation in allele frequency that have no effect on survival

Question 14

what is the relationship between population size and the effects of genetic drift

Answer 14

the smaller the population, the greater the effects of drift

Question 15

what is the source of most genetic variation in large natural sexually-reproducing populations

Answer 15

recombination due to sexual reproduction, allele shuffling during meiosis

Question 16

define: genetic natural selection

Answer 16

interactions between genetically determined phenotypes and environmental conditions that cause differential reproduction of certain genotypes

Question 17

what is an example of natural selection

Answer 17

peppered moth

Question 18

define: fitness

Answer 18

an individual’s relative ability to survive and transmit its genes to the next generation

Question 19

what are the two basic components of fitness

Answer 19

viability and reproductive success

Question 20

define: natural selection (in terms of fitness)

Answer 20

the process that progressively eliminates individuals whose fitness is low and chooses individuals of high fitness to survive and become the parents of the next generation

Question 21

how is fitness measured

Answer 21

by number of offspring

Question 22

what holds true about fitness if natural selection does not occur

Answer 22

relative fitness for all genotypes is 1

Question 23

why is selections unable to reduce the frequency of a recessive lethal allele to zero

Answer 23

when the level of the allele in the population is low, the incidence of homozygotes will be rare; heterozygotes are often unaffected or have advantages

Question 24

how does time of onset influence the frequency of disease alleles

Answer 24

diseases that cause death after the completion of reproduction will sustain little or no negative selection

Question 25

define: mutations

Answer 25

heritable changes in base sequences that modify the information content of DNA

Question 26

what are the two subclasses of base substitution mutations

Answer 26

- transition - transversion

Question 27

define: transition mutation

Answer 27

purine for purine, pyrimidine for pyrimidine

Question 28

define: transversion mutation

Answer 28

purine for pyrimidine, pyrimidine for purine

Question 29

what are the 5 classes of DNA mutations

Answer 29

1) substitution 2) deletion 3) insertion 4) inversion 5) reciprocal translocation

Question 30

define: reciprocal translocation

Answer 30

part of one chromosome has been replaced with a region from another chromosome and vice versa

Question 31

where must mutations occur to be passed on to future offspring

Answer 31

germ cells

Question 32

how was the Luria-Delbruck experiment conducted

Answer 32

set up small vials of bacterial culture and let them grow for a specified amount of time then add equal portions of each culture to plates containing media along with phage

Question 33

are mutations caused by selective pressures

Answer 33

no, they occur randomly

Question 34

what did replica plating verify

Answer 34

spontaneous mutations occur naturally

Question 35

define: mutagen

Answer 35

any physical or chemical agent that raises the frequency of mutations above the spontaneous rate

Question 36

what causes mutations

Answer 36

- natural processes of deamination - UV light - errors by DNA polymerase

Question 37

define: depurination

Answer 37

removal of a purine base, allows substitution of another base during replication

Question 38

what causes deamination

Answer 38

nitrous oxide

Question 39

what does deamination cause

Answer 39

transition substitutions during replication

Question 40

how many mutated daughter cells does deamination have

Answer 40

half

Question 41

what type of mutations does ionizing radiation cause

Answer 41

deletion

Question 42

what mutation does UV radiation cause

Answer 42

thymine dimers, causing a kink in the DNA strand

Question 43

what cleaves thymine dimers in bacteria

Answer 43

photolyase

Question 44

what enzyme repairs base excision

Answer 44

glycosylase

Question 45

what does Xeroderma Pigmentosum cause

Answer 45

inactive endonuclease, excision repair cannot occur

Question 46

what type of mutation does oxidation cause

Answer 46

transversion mutation

Question 47

how often do replication errors occur

Answer 47

once per 10⁹ base pairs

Question 48

which enzymes keep the rate of replication errors low

Answer 48

proofreading activity of DNA pol I and III

Question 49

what enzyme helps DNA polymerase with mismatch repair

Answer 49

exonuclease, removes mispaired bases during synthesis

Question 50

how does mismatch repair after DNA replication occur

Answer 50

relies on tagging parental strands with methyl groups

Question 51

what are mutations that cannot be corrected

Answer 51

unequal crossing-over and transposon movement

Question 52

how does red colourblindness occur

Answer 52

deletion in red gene

Question 53

how does green colourblindness occur

Answer 53

deletion in green gene

Question 54

how does red and green colourblindness occur

Answer 54

unequal crossing-over

Question 55

how does blue cone monochromacy occur

Answer 55

deletion of long-range control element -> no transcription of red or green genes

Question 56

what are examples of somatic cell mutations

Answer 56

- persons with one blue eye and one brown eye - some types of cancer - aging