Unit 6 Flashcards
Mutations
random and heritable changes in the sequence of DNA that can no longer be repaired
Types of mutation lesions
Abasic sites
Base mismatches
modified bases
Inter/intra strand crosslinks
double strand breaks
Point mutations
single base pair changes anywhere in the DNA sequence
Types of point mutations
Base substitutions
Base deletion
Base insertion
Types of base substitutions
Transition - purine for purine or pyrimidine for pyrimidine
transversion - purine replaced with pyrimidine or pyrimidine replaced with purine
Silent mutations
new codon encodes for same amino acid
Missense mutation
new codon codes to different amino acid
Nonsense mutation
changes a coding codon to a stop codon
Frameshift mutation
removal or addition of base pairs disrupts the triplet reading frame
Mutations are _____ and ______
spontaneous and random
Spontaneous mutations arise by:
errors in DNA replication/recombination
DNA damage
Insertion of transposons
Slippage
mispairing between template and synthesized strand in regions with repetitive sequences
Most common way mutations are introduced to DNA
mispairing of nucleotides
What does tautomerization of nucleotides lead to?
purine-pyrimidine mismatches and transition mutations
Klenow fragment
DNA polymerase proofreading
What does ionization of nucleotides lead to?
purine-pyrimidine mismatches
depurination
lose of purine base because of hydrolysis of the sugar/base bound
deamination
removal of amine group from C, A, and G by hydrolysis
when does DNA damage become a mutation
a DNA lesion is not corrected by endogenous repair mechanisms
mutagen
a chemical or physical force that can increase the mutation rate
What can mutagens do
replace base pair in DNA strand
chemically alter base pair leading to mismatch
damage a base pair so it cant pair with other nucleotides
Types of mutations (origin and frequency)
Spontaneous
Induced
Spontaneous mutation
mistakes during replication
Induced mutation
caused via known chemical and physical agents
