T4M4- DNA mutations and applied lecture Flashcards
are mutations always bad?
no they can cause either destructive cellular responses, beneficial adaptations or be perfectly harmless
what can mutations be a result of
environmental factors, spontaneous mutations or error in DNA replication
what are the most common types of mutations?
spontaneous
do viruses have low or high mutation rate?
high
why are RNA viruses more prone to mutation
due to delicate nature of backbone
- no proofreading capability
what will happen to a division of cell with mutation?
new cell will have part of mutation
what happens if a mutation occurs in non dividing (post mitotic) cell in G0 phase?
effect of mutation is negligible
are mutations inherited in somatic cells?
no
are mutations inherited in germ cells? why
yes because germ cells produce offspring
what did joshua and esther lederberg’s experiment in 1952 show
mutations are random and not directed
what type of nutrients were in the experimental setup of lederberg
nonselective supplemented nutrients
- so that cell can grow and form bacteria
what was in the new selective plate?
antibiotic penicillin
what is this process of stamping called
replica pleating
- preserves relative arrangements of colonies relative to original plate
what did they find after stamping
only few colonies survived penicillin on plate 2
what did they predict about the new colonies that survived
carry mutation resistant to antibiotic for penicillin
what does the process of replica mean
original colony isolated from original agar and used to test
after testing what did they discover about the mutations?
it existed in population prior to exposure
what can repair breaks in DNA backbone?
DNA ligase
why do most cells contain DNA ligase
for replication and repair of single stranded breaks
define proofreading
scanning DNA for potential mismatches
what does a mismatch cause
kink in DNA molecule
what causes a single stranded cleavage of mismatched DNA in the backbone
nuclease
what happens once nuclease cuts the backbone
another enzyme removes successive nucleotides from DNA strand
what happens if DNA accidently incorporates uracil
DNA-uracil glycosylase will cleave uracil from backbone, leaving deoxyribose sugar with no base
what is the lack of base detected by
AP endonuclease
what does AP endonuclease do
cleaves backbone of lack based area, leaving gap for addition of new nucleotide