Ch 6 Flashcards
Semiconservative replication
Both strands can be used to replication, one old and one new strand product
Meselson and stahl experiment proved
That DNA replication is semi conservative
Enzyme that catalyzes DNA replication
DNA polymerase
Replication adds nucleotides at what carbon
3’
In replication, the cleave of triphospahte nucleotides creates
Energy to make reaction energetically favorable
Leading strand is
Continuous, no new primer needed
Lagging strand
Fragmented and together
Semi discontinuous
One strand is continuous and the other is discontinuous, continuous
4 repeated lagging strand steps
Primer synthesis, elongation, primer removal, joining of fragment
Replisome
Multiprotoen machine with a suite of basic enzymatic function
– Helicase
– Primase
– DNA polymerase
– 3’ to 5’ exonuclease.
Protein associated with replisome
Helicase, primate DNA poly, 3’ to 5’ exonuclous
DNA poly I (bacterial)
Primer removal, fills gap in fragment, involved in nucleotide excision repair pathway, turns ribose in deoxy
DNA poly I subunits and its activities
Knlenow fragmens
5’ to 3’- polymerase activity (add nucleotides)
3’ to 5’ prime exonuclease activity (fix mistakes)
2
5’ to 3’ exonuclease activity (removed primers)
DNA poly III
Main replicative polymerase,
5’ to 3’ polymerase activity
3’ to 5’ exonuclease
DNA poly II, IV, V
DNA repair mechanisms
origin of replication (OriC)
Sequence of DNA that allows for replication to begin
Bacteria origin of replication
One
E. coli initiator protien
dnaA, only binds to negativity supercoiled origin DNA
DNA helicase (dnaB) (bac)
Unwinds helix using ATP
Sliding clamps (bacteria)
tether DNA poly to the DNA
Clamp loader (bacteria)
Use ATP to open and close clamp on DNA
Single strand bind protien
Keep dna from resealing after helicase, protect nuclease attack
Primase makes
RNA primers
DNA poly III adds to dna by
Catalyzing phosodiester bond formation between nucleotides
DNA ligase
Seals up phosodiester link between fragments
Topoisomers
Same DNA, different form (linking number and mobility in gel electrophoresis)
Topoisomerase I
Caused one break in DNA, Detangle, no ATP needed
Bacterial type I topo
Relax neg supercoil
Eukaryotic type I topo
Relax negative and positive supercoiling
Type II topo
Two breaks, both positive and negatives, unknot, decatenate entangled DNA molecules, ATP needed,
Bacterial gyrase
Negative supercoiling, a type of topo
Leading strand is discontinuous when
DNA poly III, DNA poly collide with RNA poly
How many Euk origin of rep
Many
ARS autonomous replicating sequences (yeast)
Original of replication
Mammalian origins are - rich
AT, no common consensus sequence
Rate of replication is dependent on
Number of origins activated
Replication factories
Where we expect to find replication forks and lots of replication
ORC
Origin recognition complex- euk
(euk)For replication to start, - binds to the origin. This process is ATP -
ORC and Cdc6 , dependent
G1 phase
Origin selection
S phase
Replication
Replication licensing protien
MCM2-7 helicase in complex with CDt1 (2),
CMG helicase complex
Cdc45 and GINS plus MCM2-7 inactive hexamer, loaded on leading strands
Cyclin depends kinases (CDKs)
Controls licensing of origins, activators of cell cycle transitions
Low CDK activity
Mcm2-7 can load
CDK high (s and g2)
Origins fire, but don’t reload
Initiator DNA (idna)
Yea idk in the primer?
Polymerase switching
Hand of DNA from one poly to another
PCNA
proliferating cell nuclear antigen- clamp, keeps poly from falling off
RFC- replication factor C
Loads clamp
alt methods of circular DNA replication
rolling circle rep,
rolling circle rep
(plasmid and bacteria) dsDNA is nicked, and free 3’ OH is used for replication. one strand is displaced
telomere repetitive sequence
huaman- TTAGGG
tetrahymena- TTGGGG
telomeres
allows chromo to remain linear, protect ends
c strand
shorter strand after primer is removed
g strand
overhanging pice after primer is removed
telomerase (RNP)
solves the lagging strand problem
telomerase RNA
telomerase RNA component (TERC)
telo protein part
Telo reverse transcriptase (TERT)
how does telo care of overhang
elongates C strand and folds the shit around and bonds to shorter one
shelterin
prevents telo from fusing together, coats t loops
TZAP
will bind where shelterin isn’t and cut that bitch out
as we age, telomeres get
shorter
hay flick limit
little telomerase activity limit, no longer divides
senescent
doesn’t divide
proof for telomeres linked to age
- adding hTERT allows cells to escape hayflick limit
- mice with no telo RNA looked old asf when they’re young
- mice liver thingy (fucked up bruh)
dykeratosis congenita
loss of telo activity, aging syndrome (greys, hair loss, fucked)
two forms of dyskeratosis congenital
autosmal dom, x linked
Bidirectional replication
both ways, has two forks
bacterial DNA poly
- DNA Pol I
- DNA Pol II
- DNA Pol III
- DNA Pol IV
- DNA Pol V
bacterial II IV V function
Involved in DNA repair mechanisms
DNA poly alpha
primase activity
Chromosomal DNA replication
aphelia Epsilon delta
Initiator protein (DnaA)
binds to OriC
RPA
maintains single strand in euk
fen-1
primer removalt