Gene mutations and DNA repair Flashcards
suppressor mutation
mutation that hides or suppresses the affect of another mutation
spontaneous replication errors
purine and pyrimidine bases exist in different forms called tautomers
tautomer
alternate chemical form which differs by the shift of a single proton in the molecule
cause of insertions and deletions
-strand slippage during replication
-unequal crossing over
spontaneous chemical damage
depurination: loss of purine base from a nucleotide
deamination: loss of an amino group, alters DNA bases
radiation
greatly increases mutation rates in all organisms
pyrimidine dimer
radiation mutation
-two thymine bases block replication, results from UV light exposure
transposable elements (TE)
sequences that can move about the genome
transposition
movement of the transposons
inverted terminal repeats (ITR)
DNA sequences 9-40 bp long
open reading frame (ORF)
codes for enzyme transposase
short direct repeats (DRs)
created as a consequence of TE insertion process
retrotransposons
transposable elements (TE) that amplify and move within the genome using an RNA intermediate
mismatch repair (MMR)
rarely used
-corrects errors incase pairing and small insertions/deletions
base-excision repair (BER)
fixes damaged or modified bases
nucleotide-excision repair (NER)
removes large DNA segments
double stranded break repairs
-nonhomologous end joining (NHEJ)
-homologous recombination (HR)
non-homologous end joining (NHEJ)
when there are no homologous chromosomes so the ends are glued back to any random free end
*not accurate
homologous recombination (HR)
using a sister chromatid (homologous chromosome) to synthesize new DNA to fill in break
