Mutation and Transformation

Question 1

Mutations

Answer 1

Mutations: induced by environment or spontaneous

Question 2

Spontaneous

Answer 2

Spontaneous – infrequent and random, rare due to repair mechanisms

Question 3

Spontaneous: Base substitution

Answer 3

Base substitution – most common, during DNA synthesis, point mutation

Question 4

Spontaneous: Missense

Answer 4

Missense – amino acid substitution

Question 5

Spontaneous: Nonsense

Answer 5

Nonsense – change to a stop codon

Question 6

Spontaneous: Frameshift

Answer 6

– changes reading frame over to affect all amino acids downstream

Question 7

Spontaneous: Transposable elements –

Answer 7

Transposable elements – mobile sections that are cut and reinserted into genome

Question 8

Induced

Answer 8

Induced – enhanced rate of mutation by chemicals, transposition or radiation

Question 9

Induced: UV light

Answer 9

UV light → covalent thymine dimers → DNA distortion

Question 10

Induced: Radiation

Answer 10

Radiation → DNA strand breaks,

Question 11

Induced: Chemical

Answer 11

Chemical - base analogues, alkylating agents, nitrous acid

Question 12

Induced: Intercalating agents

Answer 12

Intercalating agents – ethidium bromide, inserts between bases to create and space → frameshift

Question 13

Induced: Transposons

Answer 13

Transposons → knockout mutation

Question 14

Direct DNA Repair

Answer 14

Direct repair – photoreactivation, methyltransferase, guanine oxidation repair

Question 15

DNA Excision Repair

Answer 15

Excision repair – for bulky groups

Question 16

DNA Mismatch Repair

Answer 16

Mismatch repair – endonuclease cuts out nucleotides → DNA polymerase fills the gap → DNA ligase seals

Question 17

DNA SOS response

Answer 17

SOS response – new DNA polymerase, error prone repair, after extensive DNA damage

Question 18

Genetic Exchange

Answer 18

Genetic exchange: quite promiscuous, horizontal gene transfer

Question 19

Genetic Exchange Features

Answer 19

Features – donor → recipient only, partial transfer

Question 20

Genetic Exchange Transformation

Answer 20

Transformation – uptake of DNA from donor/environment, depends on DNA size/state and recipient competence

Question 21

Gram Negative Transformation

Answer 21

Gram negative – only uptakes DNA that is similar → binds via transformasome

Question 22

Gram positive

Answer 22

Gram positive – quorum sensing → dsDNA bound → recombination only if similar