DNA Mutations Flashcards
Mutation
any permanent change in the DNA sequence
caused by replication errors, spontaneous mutations, and radiation and mutagens
ultimate source of genetic variation, sometimes advantageous
Replication Error
intrinsic cause of mutation; polymerase introduces the wrong nucleotide and doesn’t fix the error
Radiation and Mutagens
chemical that increases mutation rate
UV lights, radiation
Intrinsic Causes of Mutation
- normal cell metabolism (free radicals) cause oxidation
- hydrolysis (deamination of cytosine to uracil, deamination of 5-me cytosine to thymine, depurination of guanine)
- replication errors
- base analogs
Extrinsic Mutagens
- UV light can cause thymine dimers
- chemicals can cause alkylation, adding bulky adducts (ethidium bromide intercalation)
- radiation
Deamination
cytosine->uracil (sometimes Thymine)
amine group on cytosine interacts with water and comes off
Depurination
guanine -> OH group
base leaves completely
Oxidation
can also damage bases, caused by free radicals created in cell metabolism
Thymine Dimers
caused by UV radiation
can prevent DNA replication from occurring, must be fixed to avoid damage
considered a bulky lesion
Intercalating Agents
considered bulky adduct
agents that can wedge themselves into and crosslink DNA
cause insertions and deletions
can be caused by chemotherapeutic agents
Double Strand Break
can be caused by chemotherapeutic agents, ionizing radiation (X-rays), oxygen, free radicals
Base Analogs
causes point mutations
enol vs keto tautomers
Transition
purine -> purine
pyrimidine -> pyrimidine
less likely to cause AA change
Transversion
purine -> pyrimidine
pyrimidine -> purine
more likely to cause AA change
