L8 DNA and replication Flashcards
out of ATGC, which are purine nucleotides?
which are pyrimidine?
A and G = purine (a cyclohex and cyclopent)
T and C = pyrimidine
why are purines and pyrimidines compatible with X-ray data?
the thickness of both a purine and pyrimidine is perfect because two of each is either too thick or too thin
what are many important aspects of DNA structure?
-opposite polarity of the two strands
-two strands joined by H-bonds between bases
-adjacent nucleotides on the same strand joined by phosphodiester bond
-hydrophobic “bonds” between adjacent base pairs form a hydrophobic core in the center of helix
what are the 3 proposed alt models of replication?
semiconservative, conservative, dispersive
S- one parent w one daughter
C-parent strands repair and daughter repair
D-strands mixed together
what direction is the replication from a single origin in prokaryotes?
bi-directional
what does DNA helicase do?
catalyzes the unwinding of parental double helix
what does DNA-binding protein (SSB) do?
keeps strands unwound and ready for replication
why can unwinding DNA supercoils block replication forks?
the unwinding can cause supercoils which can block the forks
what does topoisomerase do?
catalyze controlled cleavage and rejoining of dna the prevents OVERWINDING
3 important properties of DNA polymerase
-catalyze addition of nucleotides to new strand
-new strand synthesized in 5’ to 3’
-needs a free 3’ OH to add new nucleotides to
is the lagging strand synthesized continuously or or discontinuously?
discontinuously
what does DNA primase make?
RNA primers
what does DNA ligase do?
joins fragments
what does the sliding clamp do?
binds polymerase 3 core enzyme to the template, REQUIRED for high levels of DNA pol3 activity
what does DNA pol 3 do?
synthesize DNA
