Sets 11 Flashcards
one start is 5-3 other is 3-5 ; 5 and 3 starts attach
what is the 5’ end attached to ?
a phosphate
what is the 3’ end attached to ?
an OH on a base pair
what is the semi conservative replication ?
in daughter molecules one strand is old and one is new
what is conservative replication ?
where one helix is new and one is old
what is a dispersive ?
a mixed of ol
what is the meselspn stahl experiment and when was it done
in 1958 it confirmed that Dna was semi conservation ; they grew bacteria with nitrogen and isolated dna
what nitrogen isotopes were used
14N 15N
equilibrium density gradient centrifugation with isolated DNA
when does DNA replication happen ?
S phase
what are the two steps of DNA replication ?
initiation and elogation
what initiates the replication of DNA
an A-T rich area on the helix
what is the 4 steps of the meselspn stahl experiment
1.grow bacteria in heavy nitrogen
2. transform some to light nitrogen and continue to grow
3. take samples peridically
what is the result of the meselspn stahl experiment
at t 0 all of it is heavy but as time goes on light > heavy
what does DNA helicase do
open up the dna helix
what does the initiator priotein do
initate replication and the opening of DNA
what does dna biding protieins do ?
keep the DNA. open
what end does DNA pol 3 extend from
a 3’ oh end
what does dna primase do ?
make RNA PRIMER
why is an RNA. primer need ?
so dna pol can add nucleotides
what does DNA. pol 1 do ?
remove RNA and fill the gaps with DNA
what does DNA ligase do ?
add the 3’ to the 5’ ends of okazaki frags with phospherdiester bonds
from which side to which side does rna pol III. & I proof read
3’ to 5’
from which side to which side does rna pol I remove RNA primer
5’ to 3’
what are the 3 problems with circular chromsome replication
- replication forks move apart
- super coiling of chromsomes
- topidomerares break
what is the telmer code
TTAGGG. 250 -1500
why most adult somatic cell dont express telomerase ?
bc they shorted at every cell divisions so gene info is not lost
