Mutagens & Mutations Flashcards
what is a free radical
unstable molecule with an unpaired outer electron
fragments of broken biomolecules
how do free radicals come to be?
normal metabolism
inflammation
UV light/ionizing radiation
tobacco smoke, pollutants in air/water
ROS
reactive oxygen species
how do we deal with free radicals?
cells have enzyme detox systems
convert oxygen free radicals into O2 + water
mutagenic chemicals
attack DNA specifically
moldy peanuts fungal toxin: aflatoxin
sulfur mustard
mutagenic chemicals used to create new mutations
ethylnitrosourea and ethylmethanesulfonate
react with bases to cause lesions
could be used to kill dividing cancer cells in chemo
two kidns of electromagnetic radiation that affect DNA
UV: base dimers
ionizing: xray/gamma ray
particulate radiation
strongly ionizing
inhalation of radioactive radon gas (55%)
basements cut from solid rock accumulate radon
chemicals in food
dark meat is a source of carcinogens
processed meat that has preservatives/nitrates
childhood leukemia (hotdogs)
5 effects of a mutation inside an ORF
silent
missense
nonsense
codon gain/loss
frameshift
point mutations cause what kind of effects
silent
missense
nonsense
silent mutation
point mutation that does not change the meaning of a codon (no coding change)
missense mutation
point mutation that change one amino acid to another
coding change
nonsense mutation
point mutation that turns an amino acid codon into a stop codon
18 codons are 1 base away from stop
which two mutation effects are caused by insertions or deletions?
codon gain/loss and frameshift
in frame: deletion/insertion of 3 bases causes codon gain/loss
frameshift: deletion/insertion of anything other than 3 bases
codon gain/loss
inserts or deletes 3 nucleotide bases (1 aa)
frameshift
changes all downstream codons and causes a new termination point
can cause a protein of any length
neutral aa changes
some aa changes and gains/losses do not affect protein function
other effects of small mutations
effects: intron splice sites
regulatory sites inside or outside of transcription units
effects on intron splice sites
introns begin with GU (RNA)/ GT and end with AG
this is how a splicosome knows where to cut
if mutate either code, might splice wrong bit
effect on regulatory site outside of transcription unit
relates to CRM
may affect TF binding site so it doesn’t bind, phenotypic effect
unequal crossing over and strand slippage produce…
duplicated sequences
unequal crossing over: meiosis
strand slippage: DNA replication
variable number tandem repeat VNTR
places in DNA where same short sequence of bases is repeated in multiple tandem copies
variation in individuals btw # of copies
unequal crossing over in meiosis requires a recombination at the VNTR site
are VNTR sites protein coding?
no, function is not clear
DNA fingerprinting
VNTR genotypes are the basis b/c differ in each individual
triplet repeat expansions
a set of genetic diseases where expansion multiplies repeats within a gene
DNA replication
repeats can be in an ORF or UTR
