Replication - 16.2 Flashcards
Replication of chromosomal DNA begins at
origins of replication
Origin of replication
Short stretch of DNA
Replication fork
Y-Shaped region where strands are unwound
Helicases
Enzymes that untwist the dbl helix at the replication forks, separating the 2 parental strands, which become template strands
ssBindingProteins
Bin unpaired DNA strands, keeping them from re-pairing
Topoisomerase
Relieves strain caused by helicase by breaking, swivelling, rejoining strands
Enzymes that synthesize DNA cannot initiate _____
the synthesis of a polynucleotide
Initial nucleotide chain produced during DNA synthesis is
Short stretch of RNA, not DNA
Primer (5-10 nucleotides long)
Primer synthesized by
Enzyme primase
New DNA will start from the ____end of the RNA primer
3’
DNA polymerases
Catalyze the synthesis of new DNA by adding nucleotides the the 3’ end of a preexisting chain
Fills in missing nucleotides
DNA replication is _____(conservation)
Semi conservative
Adenine nucleotide to make DNA
dATP
Why are the nucleotides for DNA syn chemically reactive?
Triphosphate tails have an unstable cluster of negative charge
As DNA polymerase catalyzes each dehydration RXN _______ lost.
2 phosphate groups are lost as a molecule of pryophosphate
DNA polymerase catalyzes the addition of a nucleoside triphosphate to….
the 3’ end!
A new DNA strand can elongate only in the ____ direction
5’ to 3’
After RNA primer is made, ______ starts the synthesize the leading strand
DNA pol III
Leading strand is elongated
Continuously
The _____ moves DNA pol III along template strand
Sliding clamp
Lagging strand elongates in the direction
AWAY from the replication fork
Lagging synthesized in ______
okazaki segments, discontinuously
RNA pol 1
Replaces the RNA nucleotides of the adjacent primer with DNA nucleotides
DNA Ligase
Joins the sugar phosphate backbones of the Okazaki fragments into a continuous DNA strand
Seals the free end of the new DNA to the old DNA, completing the strand
