Gene mutation and DNA repair Flashcards
Describe spontaneous vs induced mutations
spontaneous - occur naturally and randomly
induced - occur from outside influence
What is a mutation?
An alteration in dna sequence
What did the luria delbruck fluctuation test prove?
Since the number of mutations in phages fluctuated from test to test, mutations were found to be spontaneous
what is the difference between somatic and germ line mutations?
somatic occur in any cell except germ cells and aren’t heritable
germ line mutations can be inherited
What is transition vs transversion mutations?
transition - pyrimidine replaces a pyrimidine or a purine replaces a purine
transversion -If a purine and a pyrimidine are interchanged
What are conditional mutations?
depends on environment in which the organism finds itself, example is a temperature sensitive mutation
What are neutral mutations?
make up most mutations, occur in areas of genome without genes, don’t affect gene products
How are mutations caused?
mispairing causing dna polymerase to insert wrong nucleotide, replication slippage, tautomeric shifts in nucleotides, and dna base damage by depurination and deamination
What happens because of base analogs
They substitute for purines and pyrimidines during nuclei acid replication
What do alkylating agents do?
donate alkyl groups to nucleotides to alter base pairing affinity
what do acridine dyes do?
cause frameshift mutations by intercalating between purines and pyrimidines
How does UV radiation distort dna?
by introducing pyrimidine dimers
What other radiation is mutagenic?
ionizing radiation in the form of X fays, gamma rays, and cosmic rays
What is the Ames test?
uses salmonella to determine if compound is mutagenic, If many his+ revertants are present, compound is mutagenic.
What are the dna repair mechanisms?
proofreading and mismatch involving bacterial dna polymerase III, correct dna stand recongnized based on dna methylation of parental strand
postreplication repair mediated by recA protein
photoreactivation repair that removes thymines caused by UV light, not detected in humans and not essential in ecoli
excision repair that functions as a cut and paste system to remove the lesion
dna double strand break that is responsible for reannealing the two strands by homologous recombinational repair
