Lecture 29 Flashcards
initiation
where the DNA gyrase uncoils the chromosome; SSBP creates a gap; helicase unzips strands; usually starts at an AT rich area because it is easier to break apart
elongation
the addition of nucleotides to the 3’ end of a growing RNA chain during transcription
termination
site located roughly opposite oriC on circular chromosome
DNA gyrase
uncoils chromosome at a specific location called OriC (initiation site) also unlink final daughter molecules
helicase
unzips the 2 DNA strands by breaking H bonds between base pairs, creates a forked DNA molecule (replication fork
SSBP
single stranded binding proteins; bind to DNA at OriC and creates a gap between the strands
primase
must add RNA primer to each DNA strand
DNa polymerase III
slides down the strand adding complementary nucleotides
clamp
attaches DNA polymerase to the strand of primer
Clamp loader
loads protein clamp onto strand
DNA polymerase I
reads original NDA in 5’ to 3’ direction, removing primers on lagging strand
- can only add new nucleotides to pre-existing 3’ OH groups while moving towards the fork
DNA ligase
makes a reaction between 5’ OH and top O of a PO4 group, after ligase binds the two, it removes the ‘break” in the DNA strand
E. coli
prokaryotic cell with floating DNA (no nucleus); replicates through binary fission
oriC
initiation site; DNA gyrase uncoils the chromosome at this site
supercoiling
DNA inside the cell twists up like rubber band so it will fit
initiator proteins
proteins that recognize specific DNA sequence within the origin of replication, this is where helicase attaches to the template strand and starts to unwind the DNA into two strands
replication fork
helicase unzips DNA strands by breaking the H bonds between base pairs and creating a forked DNA molecule
primer
synthesizes short stretches of RNA base pairs that function as primers for DNA polymerase
antiparallel
polarity runs opposite 5’ to 3’ attached to 3’ to 5’
discontinuous
synthesis occurs in short segments called Okazaki fragments
leading strand
continuous synthesis
DNA ligase
connects Okazaki fragments
lagging strand
discontinuous synthesis
okazaki fragments
short segments in which synthesis on the lagging strand occurs
nucleotides
ATCG; complementary to template, form phosphodiester bonds, and bond with bases on template
phosphodiester bond
occurs when two of the hydorxyl groups react with hydroxyl groups on other molecules to form two ester bonds, linkage between 3 carbon atom of one sugar and 5 carbon atom of another
replisome
enzymes involved in DNA replication; the entire enzyme is composed of DNA ligase, polymerase I and III, helicase and primase
