Week 7 - Causes of Mutations

Spontaneous Mutations - 2

Replication errors

Chemical changes

Spontaneous Replication Error - 3

Incorrect base pairing

Incorporation error

Strand slippage

Incorrect Base Pairing

Unusual bases

Flexible DNA backbone

Wobble error

Incorporation Error

DNA pol adds wrong nucleotide

Strand Slippage

Hairpin loop

Strand Slippage - Insertion vs Deletion

New vs template strand

Depurination

Lose purine base

Apurinic site

Random base added - A

Deamination

Lose NH2

Deaminated C

U

Chemically Induced - 4

Base analogues

Deamination

Oxidation

Intercalating agents

Base Analogues

Look alikes

DNA pol cant distinguish

Deamination - Induced by

Nitrous acid (HNO2)

Oxidation

Oxygen free radicals attack bases + alter DNA

Oxidation - G becomes

8 oxoguanine

Pair with A

Analogues - T

5-bromouracil

Analogues - A

2-aminopurine

Intercalating Agents

Chemicals inserted between rungs + distort 3D structure

Intercalating Agents - Lead to

Insertions/deletions/frameshift

Intercalating Agents - Examples

Ethidium bromide

Agent/acridine orange

Ionising Radiation

Break dsDNA

Dislodge electrons

Non Ionising Radiation

Bases absorb UV light'

Thymine dimers

Distort DNA

Deamination vs Depurination

Hydrolysis of amino group vs glycosidic bond