dna replication and repair Flashcards
unwinding of the two strands , exposed bases , and strict Watsons-crick base pairing ( becoming the complementary strand as the double strand of dna unwinds )
semiconservative replication ( aka one parental strand and one newly seznsthesied )
dna replication requirement:
1- single strand template
2- deoxyribonucleotide triphosphate ( dNTPs of A,G,C,T ) + Mg +2
3- replisome: nucleotide protein complex that co-ordinates the replication activities numerous enzymes and proteins
4- primer w/ a free 3’ end hydroxyl group
—- is the separation of 2 complimentary strands that occurs in the origin of replication
initiation
true or false:
1- specific points where dna replication begins consensus sequence - short AT poor region
2- eukaryotes have one site of replication
1- false: rich
2- false: mutible site
from the origin 2 —- move outwards in — direction.
Active systhesis requires the assembly of — at the origin of replication
- replication forks
- opposite
- replisomes
what are the roles of protein in replisomes?
1st step : unwinding proteins
- dna helicase ( separates the double strands into a single strand to allow the dna to be copied )
- single strand binding protein SSB ( wraps the single strand of dna )
- topoisomerase ( which prevents dna from getting tangled , can cut the backbone and reform it )
2nd step : enzymes to replicate
- primase ( sytheises the short rna sequence that is complementary to the single strand of dna that serves as a template )
- dna polymerase ( sythezies the dna , works in one direction , only adds to the 3’ , copies info from the template strand to make the daughter strand )
in the dna polymerase it uses — strand of the dna as a template , it reads its template from —– and it make new dna from —-. It aligns and adds nucleotides alone the ss template which specifics the —- of the new chain aka —— , catalysis formation of —–
- single
- 3-5
-5’ - 3’ - sequence
- Watson crick base pairing
- phosphor bonds
(DNA)n + dNTP —> (DNA)n+1 + pyrophosphate ( PPi ) this reaction is driven by the subsequent hydrolysis of PPi
dna polyemrase is highly — < or equal to 1000 base/second such as: —– and —– , and dna polymerase has — activity to prevent errors such as:
- highly processive as
1- PCNA proliferating cell nuclear antigen
2- sliding camp role: it encircles the dna template and keep the dna polymerase closely associated to template as it rapidly move along , the catalyses bond formation joining < or equal to 1000base / second - it has proofreading activity as:
1- substrate specificity
2- proofreading
for the dna polymerase substrate activity its active sure can bind to all —- snf catalysis occurs when the — one is bound . The dNTP base pairs with template while the enzyme is in — and catalytically — form . the enzyme conformational change with the correct W-C pair leading to —-
- all four dNTP types
- correct
- open
- inactive
- active enzyme
3’-5’ exonuclease activity acts as —- in reverse direction as it removes the nucleotide at the — end of the new strand that are mismatched
- proofreading error correction activities
- 3’ end
the leading strand is synthesised — by the — travelling the replication form since the dna polymerase makes new copies
from 5’-3’. While the —- is sytheised discountoisly piece by piece which is what we call —-
- continuously
- dna polymerase
- lagging strand
- semidiscointous replciaropn
the lagging strand is sytheises piece by piece as the primase make a new — at the regular intervals , dna polymerase replicates the template from the primer producing a new strand in —- direction , dna is blocked by proxmity of the next primer and the result is a dna strand of 1,000bp —— , primer is — , — filled and — joined
( check slide 14 for pic)
- primer
- 5-3
- Okazaki fragments
- removed
- gaps
- backbone
in eukaryotic dna polymerase the human have multible enzymes and the main ones are:
poly alpha ,delta , and epsilon
—- is involved in initiating the replication and is associated tightly w/ primase to make a —-
poly alpha , poly alpha / primase complex that is 7-10 rna + 15dNTPs
poly alpha replicated the dna by —– 5’-3’ and it has —- and the processive is —-
- extending the primer
- no exonulceas activity aka no proofreading
- moderate
poly delta and epsilon are not associated with — and they replicate the dna by extending the primer 5-3 and their processive is — , they have — in complex with —- and they have —- activity
- primase
- high
- unlimited in complex w/ PCNA
- 3-5 exonuclease activity
— is responsible for the leading stranding synthesis
—- is responsible for the lagging strand sythesis
- poly epsilon
- poly delta
the two enzymes required for the primer removal are:
1- Rnase H1
2- Flap endoculease 1 ( FEN1 )
( check slide 17)
— removed most of the rna leaving one 5- ribonuclide adjacent to the dna
—- removes the 5- ribonucleotide which has the endonuclease activity and poly alpha lacks proofreading , and this has endoculeas activity but the mismatch is up to — from 5- end of annealed dna
- Rnase H1
- FEN1
- 15 bp
eukaryotes lack — sequence , dna replication proceeds until each replication fork — with the fork from the adjacent replicon
the problem w/ replicating the 2 ends of linear dna strands called —- , the continuous synthesis on the leading strand can proceed to very tip of the template. but what happenes to the extreme end of the lagging strand????
- primer is removed but the — available for the dna polymerase to add nucleotide so the dna can be replicated at the end of the strand ( that’s for the leading strand unlike the lagging strand it doesnt have that )
- termination
- collides
- tolemeres
- OH
3’ end of each chromosome —- of the tandem repeats which is — in humans
- 1,000
- TTAGGG
telemetric dna synthesised and maintained by — = —–
the – acts as a template for the sytheiss of the dna and adds tandem repeat to the — end
- telomerase = ribonucleoprotein ie. rna + protein
- rna
- 3’
the normal tolmerase activity is —- the cells as in unicellular eukaryotes and in humans as ——- production
1- dividing
2- germ line and gametes production as sperm
during the development as cells divide and differentiate the telomerase function —–
declines = tolermease shortens
