DNA replication Flashcards
how long are okazaki fragments in euks and proks
euks- 100-200, proks 1000-2000
what nucleotides are usually rich in Oris
AT (also lots of short repeats)
what do origin binding proteins recruit
pol III
how do helicases unwind (what bonds get broken)
H bonds between bases
Primase is a ____ dependent ____ polymerase that makes a _____ of ____ nucleotides on the ____ strand
DNA dependent RNA polymerase, makes RNA primer of roughly 10 nt on parent strand
DNA pol I in proks has 3 functions
DNA polymerase, 3-5 exonuclease and 5-3 endonuclease
DNA pol I is described as what and why
distributive, no sliding clamp and falls off often
what is the main function of DNA pol I in proks
replaces RNA primers and clean up function
DNA pol III in proks has what activity
3-5 exonuclease and DNA polymerase, does NOT have exonuclease aka it cannot remove RNA primers
pol III is called “___”
processive- makes DNA on leading and lagging strand and is the major replicative enzyme because it has the sliding clamp
ligase does what
seals okazaki fragments after pol I has replaced the RNA primers
whats the difference between topoisomerase and gyrase (aka what is the defining characteristic of a gyrase)
gyrase is a type of topoisomerase that is inhibited by quinolines and mostly found in proks
telomerase is a ___ dependent ____ polymersae that does
RNA dependent DNA polymerase that keeps chromosomal ends by copying their telomeric repeat sequence from an RNA template
how does this telomerase get it to work
telomeres are a uniform repetitive sequence
where is telomerase repressed and where is it expressed
repressed in normal somatic cells, expressed in germ line or cancer cells
example of an endogenous and exogenous reverse transcriptase
endogenous= telomerase and exogenous is in retrovirus’
what strand has the end replication problem
lagging
what does DNA polymerase require to work
RNA primer (the 3’ OH)
what direction is DNA polymerase making stuff
5-3
how are errors corrected in DNA polymerase
3-5 exonuclease
what two prokaryotic polymerases have proofreading ability
1 and 3
leading strand order of events
- origin binding proteins bind to origin, 2. DNA melted by helicases, 3. ssbp bind ss DNA, 4. topoisomerase relieves tension, 5. pol III elongates
what is the difference between leading strand origin of events
primes comes in after topoisomerases to add RNA primers and you need ligase to synthesize all of the okazaki fragments
