mutations and DNA repair Flashcards
in the following sequence of DNA, the italicized base has been mutated. What type of mutation is this?
5’- GATCTCCGAATT-3’
5’GATCTCCCAATT-3’
transvehrsion-changed pyrimidine to purine or vice versa
mutations that occur naturally as a result of natural processes are called
spontaneous mutations- result from abnormalities in cellular/biological processes
which class(es) of mutations can or do change the amino acid sequence of proteins but NEVER truncate them?
missense mutation- alter amino acid sequence
if a codon is mutated from AAA to AAg what type of mutation has occurred?
silent mutations- alter codon but does not change amino acid encoded
if a codon is mutated from UAU and UAA what type of mutation has occurred?
non-sense mutation- change codon into stop codon
a temporary change in structure of a nitrogenous base is called
a tautomeric shift-spontaneous changes in base structure can cause mutations if they occur immediately prior to DNA replication
what is the Ames tea used to determine
the mutagenicity of chemical compounds
which type of DNA repair mechanism is most important TO HUMANS in regard to removing and replacing pyrimidine dimer induced by UV light?
nucleotide excision repair- repairs thymine dimers and chromosome modification bases
one of the most frequent trinucleotide repeats involved expansion of which of the following?
A.GAA
B. CAG
C. ATg
D. any Condon containing three of the same bases
CAG
mutation
change in DNA sequence
transition
change in pyrimidine (C,T) to another pyrimidine or a purine (A,G) to another purine
(same base changes)
transversion
change in a pyrimidine to a purine or vice versa
missense mutations
alter the amino acid structure, change in codon
nonsense mutation
changes codon into a stop codon
silent mutations
alter codon but do not change the amino acid encoded
frameshift mutations
involve addition or deletion of nucleotides in multiple of 1 or 2 but not 3
up promoter mutation
increase transcription
down promoter
decrease transcription
germ-line cells
cells that are or give rise to gametes
somatic cells
any other cel mutation cannot be passed on to future generations
spontaneous mutations
result from abnormalities in cellular/biological processes
induced mutations
cause by environmental agents
deprivation in spontaneous mutations
linkage between purines and deoxyribose spontaneously break
deanimation in spontaneous mutations
cytosine and 5-methykcytosine can spontaneously reanimate to create uracil/ thymine
tautomeric shifts
temporary change in base structure and can cause mutations if they occur immediately prior to DNA replication
reactive oxidative species
used to kill immune system to kill invading cells
oxidative stress
imbalance between synthesis/destruction of ROS
mutation rate
likelihood that a gene will be altered by a mutation
photolyase repair
can repair thymine dimers
thymine dimer
2 adjacent thymine bases in a DNA strand that have become covalently linked
alkyltransferase
reapirs alkyalted bases
nucleotide excision repair
can repair DNA damages, including thymine dimers, and chemically modified bases, missing bases and some types of cross-link
mismatch repair
during DNA replication an incorrect base may be added by mistake creating a mismatch and the DNA polymerase has a 3’ to 5’ proofreading ability that can detect base mismatches and fix them
