DNA Replication Flashcards
what is the difference between DNA and RNA structures
RNA has a 2’ OH and 3’ OH where DNA only has a 3’ OH, RNA uses uracil instead of thymine
what makes RNA less stable than DNA
the 2’ OH can perform chemistry so RNA can act as a catalyst
why can you only add to the 3’ end of a nucleic acid polymer / what does this mean for polymerases
the chemistry of the OH being released when binging with a new dNTP / means that polymerases are directional
in what direction do polymerases move
5’-3’ on the primer strand and 3’-5’ on the template strand
what do all DNA polymerases need
all DNA polymerases need a primer
what can all DNA polymerases not do
they cannot make dimers
what is replication on a circular chromosome
bidirectional and semiconservative (keeps one original strand)
what is the main origin of replication in EColi
oriC
what is DnaA
the initiater protein - it binds to oriC at the 9bp sequence
what is DnaB
a helicase that unwinds the helix to expose the template strands (one one each strand) - proceeds away from oriC
what is DnaG
a primase that synthesizes RNA primers in the replisome that binds to DnaB to make the RNA primer
what is DNA pol III
the major replication enzyme brought by the clamp/clamp loader
what is DNA pol I / RNaseH
they replace RNA primer with DNA in okazaki fragments
what is DNA ligase
it seals the opening in DNA strands after DNA pol I replaces the primer (connects fragments)
what is DNA gyrase
relieves DNA supercoiling - reduces strain from the supercoil during replication
what does RNAse H or DNA pol I recognize to replace RNA
recognizes the RNA-DNA hybrid
what do topoisomerases in bacteria do
they introduce supercoils to condense DNA - allows it to fit inside the cell - causes stress and tension during replication
what do quinolones do / how do they work
they are antibiotics that block the function of DNA gyrase / they would cause too much strain on the DNA which would lead to the double strand breaking - lead to large scale mutation or cell death
what do the multiple short terminator sequences do
because bacteria is circular the replisome cannot just run off the chromosome - has to be stopped and that is what the ter clusters do
why are there clockwise and counterclockwise sequences
there has to be sequences in both directions or one side will continue to go around and the other will stop
what does the protein Tus do
binds to the ter sequences and acts as the orientation-specific counter helicase to stop replication - must be in both directions
what are the magicians of replication - they separate the loops
topoisomerase IV and XerC / XerD proteins
in slowly growing bacterial cells which is longer, the generation time or the replication time
the generation time is longer than the replication time
in rapidly growing cells which is longer, generation time or replication time
the replication time is longer than or equal to the generation time
what regulates replication frequency
the concentrations of DnaA and ATP - must be lots of both to replicate
