DNA replication Flashcards
what is ann unambiguous sequence ?
there is no ambiguity or shak where each base lies in the sequence
these are needed fo transcription and translation no room for uncertainty
what is redundant or degenerate sequences ?
certain positions can be represented by multiple possible bases
two different nucleotides pairs could give thee same amino acid
this is used in coding for amino acids
what is a codon ?
a set of three nuucleotides
what is a commaless sequencee ?
genetic cod is read continuously with no gaps which is what happens in DNA there are no gaps
what is non overlapping sequence ?
no nucleotides are shared between each codon
what is universal code ?
genetic codee is conserveed throughout evolution
what is the exception of universal code ?
mitochondria in humans
what is redundant sequence ?
ensures that different codons can code for the same protein
for example there are 20 sets of codons that can code for the sam amino acid
what is the wobbly hypothesis ?
allows for one tRNA to attach and to code for more than one set of codons
why do we neeed less tRNA than odon sequences ?
du to thee wobbl hypothesis
what ar the two amino acds that arre an exception to the reeduundant sequence theory ?
tryptophan
methioninie
in what direectioinn does DNA synthesis happen in ?
in the 5 prime to 3 prime direction
what is the difference between the leading strand and the lagging strand ?
the leading strand is made in the 5’ to 3’ direction and is mad in a continuous fashion and only requires one primer
the lagging strand is synthesized in the 3’ to 5’ direction and is made discontinuously in fragments called okazaki fragments each fragment needs its own RNA primer (( in the opposite direction off the replications fork )
what enzyme unwinds the DNA strands from each other ?
DNA helicase which is assisted by SSBP
single strand binding proteins
where does the origin of replication usually lie ?
in AT rich sequences
what syndrome is associated with a lack of helicase ?
bloom syndrome
what is the function off DNA topoisomerase and what is the difference between topoisomeras 1 and 2 ?
helps relax the supercoils avoids tangling of thee DNA strands
by cutting strands in the DNA
topoisomerase 1 : single strand breaks , no ATP needed
topoisomerase 2: double strand breaks , ATP needed
what is DNA gyrase ?
a type of topoisomerase 2 that is specifically found in bacteria
what drugs inhibit topoisomerase ?
etoposide teniposide
quinolones inhiibit top 2 in bacteria
what is primase ?
enzyme that makes RNA primers
once the RNA polymerase is in place the DNA polymerase can attach and start adding nucleotides
what is the difference between DNA polymerase 1 and 3 ?
both of these enzymes are only found in prokaryotes
1: degrades RNA primers
3: adds nuccleotides at thee 3’ end
in what direction does synthesis happen with DNA polymerase and what direction does thee proof reading process happen in ?
synthesis happens in the 5’ to 3’ direction
proof reading happens in the 3’ to 5’ direction
what is thee function of DNA ligase ?
binds thee okazaki fragments together with phosphodiester bonds
what is telomerase ?
enzyme that helps maintain thee end of telomeres
telomeres get shorter with each replication so telomerase adds DNA to the end of these telomeres to avoid them gettingto short
what is the DNA sequence added by telomerase ?
TTAGGG
