DNA damage and mutation Flashcards
DNA damage
a change to the regular chemical structure of the DNA double helix
Mutation
a permanent heritable change in the sequence of an organism genome
What are the different types of mutation?
~ point
~ chromosome
~ changes in chromosome number
~ transposon insertion
Forward mutation
wild type ‘active’ to mutant ‘defective’
Reverse mutation
mutant ‘defective’ to wild type ‘active’
True reversion
restores sequence code for the wild type amino acid in affected protein
Partial reversion
changes sequence at site of original mutation to some other aa that fully or partially restores protein function
Suppressor mutation
changes sequences at a different location from original mutation but in a way that compensates for original mutation
e.g. intragenic (within same gene) and intergenic (diff genes = interacting proteins) suppressors
Spontaneous mutation
arise without exposure to exogenous agents
Random mutation
changes that happen by chance
~ sometimes happen to be adaptive
Adaptive mutation
organisms ‘direct’ mutations to adapt to a particular environment
Does T1 phage resistance support the adaptive or random mutation theory?
both
What are the different types of mutagens?
chemical: 1) base analogs 2) base modifying agents 3) intercalating agents Physical: 1) ionising radiation 2) Ultraviolet
Transposon
a.k.a. a transposable element
is a DNA sequence that can change its position within a genome
Transversion mutation
CG to GC
Transition mutation
AT to GC
Missense mutation
changes from one amino acid to another
Nonsense mutation
changes from an amino acid to a stop codon (TAA, TAU, TGA)
Neutal mutation
change one amino acid to another with similar chemical properties
Silent
change in codon but same amino acid is specified
Name the 7 types of point mutation.
Transition, transversion, missense, nonsense, neutral, silent and frameshift
Difference between endogenous and exogenous damage?
endogenous = spontaneous exogenic = environmental
