block a lec 3

Question 1

what is a mutation

Answer 1

heritable change in DNA seq that can lead to a change in phenotype

Question 2

what is a mutant

Answer 2

a strain of any cell or virus differing from parental strain in genotype

Question 3

what is a wild type strain

Answer 3

typically refers to strain isolated from nature

Question 4

why is perfect fidelity couterproductive

Answer 4

prevents evolution

Question 5

what are selectable mutation

Answer 5

those that give the mutant a growth advantage under certain conditions

Question 6

what are non selectable mutations

Answer 6

those that have neither an advantage nor disadvantage

Question 7

what is screening

Answer 7

detecting mutations by examining a large no of colonies and looking for differences

Question 8

what are induced mutation

Answer 8

those made environmentally or deliberately

Question 9

how can induced mutations occur

Answer 9

results from exposure to natural radiation or oxygen radicals

Question 10

what are spontaneous mutations

Answer 10

those that occur without external intervention

Question 11

what are point mutations

Answer 11

mutations that change only one base pair

Question 12

what can point mutations lead to

Answer 12

single aa change in a protein and an incomplete protein

Question 13

what is replica plating useful for

Answer 13

identifying cells with a nutritional requirement for growth
auxotroph

Question 14

what is a silent mutation

Answer 14

does not affect aa sequence

Question 15

what is a missense mutation

Answer 15

aa changed
polypetide altered

Question 16

what is a nonsense mutation

Answer 16

codon becomes stop codon, polypeptide is incomplete

Question 17

when are nonsense mutations more likely to cause damage to phenotype

Answer 17

closer the mutation is to the beginning of the polypeptide

Question 18

what are frameshift mutations

Answer 18

deletions or insertions that result in a shift in the reading frame

Question 19

what do frameshift mutations often result in

Answer 19

complete loss of gene function

Question 20

what type of mutation is typically reversible

Answer 20

point mutations

Question 21

what is reversion

Answer 21

alteration in DNA that reverses the effects of a prior mutation

Question 22

what does revertant mean

Answer 22

strain in which original phenotype is restored

Question 23

what are the 2 types of revertant

Answer 23

same site revertant
second site revertant

Question 24

what is same site revertant

Answer 24

mutation is at the same site as og mutation

Question 25

what is second site revertant

Answer 25

mutation is at a different site in the DNA

Question 26

what is a suppressor

Answer 26

a mutation that compensates for the effect of the original function

Question 27

what genome has higher mutation rate

Answer 27

RNA genome 1000 fold higher

Question 28

what is one of the first tests that new drugs undergo

Answer 28

Ames test

Question 29

what is the Ames test

Answer 29

makes practical use of bacterial mutations to detect potentially hazardous chemicals looks for an increase in mutation of bacteria in the presense of suspected mutagen

Question 30

what is frequency of error in DNA replication

Answer 30

10^-6 to -7

Question 31

why are there new variants of the cold every year

Answer 31

because RNA pol doesnt often have proofreading abilities

Question 32

what are mutatgens

Answer 32

chemical, physical, or biological agents that increase mutation rates

Question 33

what are nucleotide base analogs

Answer 33

they resemble nucleotides and mispair nucleotides

Question 34

what can chemical mutagens induce

Answer 34

chemical modifications nitrosoguanidine

Question 35

what are the 2 main categories of mutagenic electromagnetic radiation

Answer 35

nonionising and ionising

Question 36

example of nonionising EMR

Answer 36

UV radiation

Question 37

examples of ionising NMR

Answer 37

X rays, Gamma rays, cosmic rays

Question 38

what strongly absorbs UV

Answer 38

purines and pyrimidines

Question 39

what is one effect of UV rad

Answer 39

pyrimidine dimer

Question 40

what can be ionised and produced

Answer 40

water to produce free radicals

Question 41

what do free radicals damage

Answer 41

damage macromols in the cell

Question 42

what are the 3 types of DNA repair systems

Answer 42

direct reversal repair of single strand damage repair od double strand damage

Question 43

what is direct reversal

Answer 43

mutated base is still recognisable and can be repaired without referring to other strand

Question 44

what is repair of single strand damage

Answer 44

damaged DNA is removed and repaired using opposite strand as template

Question 45

what is repair of double strand damage

Answer 45

a break in DNA requires more error prone repair mechanisms

Question 46

what system is used when DNA damage is large (interferes with DNA rep)

Answer 46

SOS regulatory system

Question 47

what does translesion synthesis allow

Answer 47

DNA to be synthesised with no template

Question 48

what type of activity does RecA have

Answer 48

protease activity

Question 49

what is RecA induced

Answer 49

when cell senses DNA damage

Question 50

what is the role of RecA

Answer 50

to degrade LexA

Question 51

what dos LexA do

Answer 51

sits and blocks DNA repair promoters

Question 52

what is recombination

Answer 52

physical exchange of DNA between genetic elements

Question 53

what is homologous recombination

Answer 53

process that results in genetic exchange between homologous DNA from 2 different sources

Question 54

what is selective medium used for in homologous recombination

Answer 54

to detect rare genetic recombinants

Question 55

what is the only way to repair a double stranded break

Answer 55

homologous recombination

Question 56

what are transposable elements

Answer 56

discrete segments of DNA that move as a unit from one location to another within other DNA mols

Question 57

how are transposable elements moved

Answer 57

transposition

Question 58

who first observed transposition

Answer 58

barbara mcclintock

Question 59

what are the 2 main types of transposable elements

Answer 59

transposons insertion sequences

Question 60

what are the simplest transposable elements

Answer 60

insertion sequences

Question 61

size of IS

Answer 61

~1000 nucleotides inverted repeats are 10-50 base pairs

Question 62

where are IS found

Answer 62

in plasmids and Chr of bacteria and archaea and some bacteriophages

Question 63

how do transposase move DNA

Answer 63

between inverted repeats

Question 64

what does the insertion of a TE generate

Answer 64

duplicate target seq

Question 65

what are the 2 mechanisms of transposition

Answer 65

conservative and replicative

Question 66

what is a conservative mechanism of transpositon

Answer 66

where transposon is excised from one location and reinserted at a second location no of transposons stays constant

Question 67

what is a replicative mechanism of transposition

Answer 67

a new copy of transposon is produced and inserted at a second location number of transposons present doubles

Question 68

how can gene be recovered in transpositon

Answer 68

transposons can be tagged, the AMR marker

Question 69

what does it mean if a cell is capable of growing on selective med.

Answer 69

likely acquired a transposon

Question 70

what is CRIPSR

Answer 70

clustered regulatory interspaces short palindromic repeats

Question 71

how is CRISPR carried out

Answer 71

-cuts DNA, double stranded break -repair fragment DNA and in middle as AMR marker -homolog recombin -mutant at that precise place can be identified from AMR marker