Week 2 DNA mutation & molecular biology techniques Flashcards
What is mutation
Permanent change in DNA sequence
Causes: Errors in DNA rep/repair or by induced mutations e.g chemicals, radiation or viruses
e.g cystic fibrosis CFTHR gene
Sig: Evolution disorders can study gene function
Haploinsufficiency
Motor loss
Gain of function explained
Chromosome rearranged, new function but may not respond to negative effects
Base excision repair
Fixes singular base
DNA glycolase removes the base, AP endonuclease cuts DNA , DNA polymerase adds new base, Ligase seals the gap
Nucleotide excision repair mechanism enzymes
uvra,b,c,d and helicase 2 uvrD
Fixes distortions caused by dimers
Proteins detect distortions, damaged strands excised by endonuclease, DNA polymerase fils gap ligase seals
Homologous recombination
Repairs a split in DNA strand
New single strand DNA is produced, new strand joins old one, DNA polymerase fils the gap and ligase seals
Missense mutation
Single nucleotide change, causes different AA in the protein
Frame shift
Add/del of nucleotide
Silent mutation
Doesn’t affect AA being encoded, only changes the nucleotide sequence
Restriction enzyme
recognises a particular set of sequences which then cuts them
Maxam gilbert method
Cleaves dna strand at different bases use gel elctrophoerisis to separate strand to be then viewed
Cloning
Exact replication of DNA by DNA polymerase
Microarray
- Used in gene expression detects mutations, diagnostics
- Analyse many genes but low sensitivity and possible to get false results
DNA damaging agents
External: UV - produces dimers that distort DNA (sun)
Ionising - X-rays, breaks DS (nuc radiation)
Chemicals, viruses integrates with host gene
Internal: Oxidative stress, rep errors and deamination
Non-homologous recombination
Repairs DS breaks
Recognised by specific proteins, DNA end that aren’t broken are extended, DNA ligase seals
small scale mutations
Point mutation, only affects a few nucleotides
nonsense mutation
Converts a codon to a stop codon halting the protein production
