DNA Replication Flashcards
DNA metabolism consists of a set of ___ regulated processes that achieve: ___ ___ ___ (synthesized with high fidelity before each cell division), errors during synthesis are ___ and ___, segments are ___ either within a chromosome or between two DNA molecules to give offspring novel DNA
tightly/new DNA copy/checked/repaired/rearranged
The three fundamental rules of DNA replication are:
1) replication is ___
2) begin at the ___ and proceed ___
3) synthesis occurs ___’ to ___’
semiconservative
origin/bidirectionally
5/3
An experiment that used differently weighted N isotopes to determine that the semiconservative model (with one daughter strand and one parent strand) in DNA is correct because of the intermediate hybrid band
Meselson-Stahl experiment
Cairn’s experiment:
shows how circular DNA replicated, radio labelled DNA and took pictures which shows an extra loop and both strands replicating simultaneously and bidirectionally
Inman’s experiment:
denatured DNA to form bubbles and proved loops always initiate at a unique location, the origin of replication
New nucleotides are always added to the ___’ end
3
the leading strand is replicated ___ and ___ the fork while the lagging strand is replicated ___ and ___ the form
continuously/towards/discontinuously/away from
Okazaki fragments
fragments of replication along the lagging strand which are eventually joined to make a complete strand
The steps of elongation are:
1) parental DNA is used as a template
2) nucleoside triphosphates act as substrates
3) 3’ -OH on the chain attacks the α phosphate of the incoming trinucleotide
4) pyrophosphate is released
Primer: required by DNA polymerase, short strand that is ___ to the template, contains a ___ to begin the reaction, can be either DNA or RNA
complementary/ 3’-OH
What are the three sites and their roles on DNA polymerase?
1) insertion site: where incoming nucleotide binds
2) post-insertion site: where newly-made base pair resides
3) active site: excludes any base pairs with incorrect geometry
How would the geometry of the base pairs be incorrect?
If the wrong pair was inserted
3’-5’ exonuclease:
proofreads and corrects any errors made by DNA polymerase
Which version of DNA polymerase does the same thing as 3’-5’ exonuclease? How?
DNA polymerase I, it moves ahead of the enzyme and hydrolyzes things in its path which allows the nucleotides to be removed and replaces if needed
Which DNA polymerase is the principle replication polymerase?
III
Which enzymes are required for e.coli DNA replication and what are their functions?
1) helicase: use ATP to unwind DNA
2) topoisomerase: relieve stress from unwinding
3) DNA-binding PRO: stabilize separated strands
4) primase: make RNA primers
5) DNA ligases: seal nicks between successive nucleotides to make the strand complete
What is the name of the site the replication begins at?
The oric site
R sites:
5 repeats fo a 9BP sequence that bind the initiator
DUE:
A/T rich region, DNA unwinding element
Leading strand elongation (circular): ___ makes primer, polymerase ___ adds nucleotides to the ___’ end, pol ___ is linked to DNAb which is tethered to the ____ ____
primase/III/3/3/opposite strand
Lagging strand elongation (circular): ___ make primer and pol ___ adds nucleotides to the ___’ end, strand is elongated ___ the fork.
Primer is removed by ______ which also fills in the gaps, DNA ___ seals the backbone
primase/III/3/away from/DNA pol I/ligase
What are the three stages of DNA replication?
Initiation, elongation, termination
What are the steps of termination for circular DNA?
1) replication site meets Ter site which it is unable to leave from
2) Ter binds the termination utilization sequence
3) Chromosomes are left as catenanes (topologically interlinked circles
4) DNA topoisomerase IV separates the catenanes by breaking the strands of one to allow the other to leave
