module 7 Flashcards
DNA replication
the process by which genetic material is copied
AT/GC Rule
A pairs with T and G pairs with C
parental strands
the two original DNA strands
daughter stands
the two newly-made DNA strands
Semiconservative model
double-stranded DNA contains one parental and one daughter strand following replication
Bacterial DNA Replication
origin of replication (only one per chromosome), synthesis of DNA proceeds bidirectionally with the replication forks eventually meeting on the other side.
oriC DNA sequences
DnaA boxes, AT-rich regions, GATC methylation sites
DnaA boxes
sites for the binding of DnaA protein
AT-rich regions
sites where the DNA strands separate
GATC methylation sites
sites that help to regulate DNA replication
DnaA proteins
cause the DNA to bend
DnaB/helicase
binds to the origin and further separates DNA strands
Dam
prevents second round of replication from occurring to quickly after the first one by taking several minutes to methylate the A on both strands post replication
unwinding of the helix
DNA helicase separates strands by breaking hydrogen bonds, DNA gyrase/Topoisomerase 2 alleviates positive supercoils
Single-strand binding proteins
bind to the separated DNA strands to keep them apart
RNA primers
allows DNA polymerase to bind to strand and synthesize DNA
primase
creates RNA primers
DNA pol 1 and 3
normal replication
DNA pol 2, 4, 5
DNA repair and replication of damaged DNA
DNA pol 3 holoenzymne
alpha subunit catalyzes bond formation between adjacent nucleotides, beta subunit forms a dimer around the template DNA for movement
DNA pol 1
removes the RNA primers and replaces them with DNA
Okazaki fragments
DNA fragments on the lagging strand
DNA ligase
catalyzes the formation of a covalent bond to connect the DNA backbones
primosome
DNA helicase and primase bound together
replisome
primosome + two DNA polymerase holoenzymes
termination sequences
when bound to tus, stops the movement of the replication forks
T1
stops counterclockwise forks
T2
stops clockwise forks
catenanes
intertwined circular molecules from DNA replication that are separated by DNA gyrase
temperature sensitive mutant
can survive at a permissive temp but will fail to grow at a nonpermissive temp
formation of covalent bond
innermost phosphate group of the incoming DNuclioside triphosphate and the 3’-OH of the sugar of the previous DNucleotide
high fidelity
stability of base pairing, structure of the DNA polymerase active site, proofreading function of DNA polymerase
DNA replication in eukaryotes is more complex because…
large linear chromosomes, chromatin is tightly packed within nucleosomes, more complicated cell cycle regulation
eukaryotic origins of replication
ARS
prokaryotic origins of replication
OriC
ARS have
~50 bp, high percentage of A and T, have a copy of the ARS consensus sequence (B1 and/or B2)
ATTAT(A or G)TTTA
B1 and B2
ARS consensus sequences
enhance the function of origin of replication, separation of strands occurs in B2, are found within a nucleosome-free region
Origins of replication in complex eukaryotes
G4 motifs, promoters and CpG islands
classes of replication origins in complex eukaryotes
constitutive, flexible (most common), dormant
constitutive OoR
used all the time
flexible OoR
used in a random manner
dormant OoR
used during cell differentiation or only at a specific stage of development
flap endonuclease
removes the primer
telomeres
DNA end sequence that prevent chromosome shortening
telomerase steps
binding, polymerization, translocation
