DNA replication Flashcards
information is copied during ____ and distributed during ____.
interphase
cell division
parts of the cell cyle
G1 to S to G2 to mitosis
period of cell growth before the DNA is duplicated
gap one (G1)
period when the DNA is duplicated
synthesis phase (S phase)
period after DNA is duplicated and cell prepares for division
gap two (G2)
G1, S, and G2 make up the
interphase
four general characteristics of DNA replication
chemically uni-directional
semi-conservative
spatially bi-directional
semi-discontinuous
scientists that proved DNA replication was semi-conservative
meselson and stahl
DNA replication occurs in specific nuclear or nucleoid compartments
replication factories
the region of DNA that first separates and replication begins
origins of replication
DNA replication proceeds in both directions away from the origin of replication
bi-directional replication
the point of separation of double-stranded DNA at which incorporation of nucleotides occurs during DNA replication
replication fork
where each separated polynucleotide strand serves as a template for the synthesis of a single new complementary strand
semi-conservative replication
the synthesis of DNA fragments that occurs in the lagging strand during DNA replication
semi-discontinuous replication
the name given to the discontinuous fragments of DNA synthesized in the lagging strand
okazaki fragments
five basic steps for DNA replication
- helicase unwinds parental double helix
- single stranded binding proteins stabilize unwound DNA
- leading strand is synthesized continuously in 5’ to 3’ direction by DNA polymerase
- lagging strand is synthesized discontinuously by RNA primase laying a primer down so DNA polymerase can form an okazaki fragment
- DNA ligase joins okazaki fragments
unwind and stabilize the duplex DNA to form the replication fork
initiation
DnaA proteins bind to origin of replication
initiation factors
DnaB protein catalyzed the ATP-dependent unwinding of duplex DNA
helicase
prevent supercoiling and tangling of DNA during unwinding; binding ahead of the replication fork, nick super coiling DNA, and relaxes stress allowed by uncoiling
topoisomerases
prevents re-annealing of the separated single strands, protects against nuclease degradation
ssDNA binding proteins
5’ to 3’ synthesis of complementary DNA
replication
an RNA polymerase synthesizes a short RNA primer
primase
extends the RNA-primed chain and is the main replication enzyme
DNA polymerase III
later replaces RNA with DNA and using 3’ to 5’ exonuclease activity to ensure accuracy
DNA polymerase I
joins DNA fragments
DNA ligase
subunits of DNA polymerase that use ATP to load DNA into the beta clamp unit
tau
gamma
beta
beta prime
hold/guides DNA, opens and closes to allow passage of DNA in DNA polymerase
beta sliding clamp
an enzyme that removes nucleotides from the end of a polynucleotide strand
exonuclease
subunit of DNA polymerase that performs 5’ to 3’ polymerase reaction
alpha subunit
subunit that performs exonuclease
epsilon subunit
what makes up the DNA replicating machine called a replisome
two copies of DNA polymerase III
primosome DNA unwinding proteins
contains primase and auxiliary proteins
primosome
repair enzymes normally present in cells where they repair low levels of DNA damage
DNA polymerase II and IV
bind to sites on opposite side of DNA loop, inhibit helicase and prevent further progression of replication fork (in prokaryotes)
ter binding proteins
play a role in replication termination in eukaryotes by preventing the ends of DNA from being lost
telomeres
an enzyme that restores telomere sequence
telomerase
how does telomerase work
extends the unreplicated end so the lagging strand can be completed
