BIO 326R 1st Edition Lecture 9Outline of Last Lecture I. Fermentation vs. RespirationII. Anaerobic Growth and Aerobic GrowthIII. Respirationa. Establishes pmfb. F0F1 ATPaseIV. Pmfa. Synthesize ATP and transportb. Respirators vs. fermenters use of pmfOutline of Current Lecture I. HistoryII. Bacterial chromosomesa. Steps to replicationIII. Initiation of synthesis and synthesis mechanismCurrent LectureHistory- More on info sheet on blackboard- DNA discovery experiments were done on bacteria- Linus Pauling won Nobel Prize for proposing triple helix structure in 1951These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Roslind Franklin proposed DNA double helix structure with X ray crystallography photoo Used more purified DNA, so this structure was quickly adapted- Oregan State University has the Pauling Paperso Letters to his wife and scans of his notesBacterial Chromosome Replication- Circular (most—but some are linear), double stranded- Steps to replicationo Find origin of replication DnaA binds to OriC- OriC= origin, defined sequence, 13 bp repeat- DnaA= protein that locates OriCo Unwind DNA Helicase and DnaB- Use ATP for energy DnaC- Helps DnaB find DnaA-oriC complex- Unwinding at OriCo A/T rich where unwinding occurs A-T has 2 hydrogen bonds rather than the 3 in G-C, so is lower energy and easier to unwind Replication bubble- Unstable—could rebind and close replication fork- Need to stabilize to stay openo Single strand binding proteins= binds single strand DNA and stabilizes the replication forko Assemble replisome Bring in all replication machinery DNA Polymerase I (abundant—400/cell)- RNA polymerase removal DNA Polymerase III (not abundant)- DNA replication- Can synthesize about 1000 nucleotides per secondo Bidirectional for efficiencyo E. coli is 4.5 million base pairs, so it takes about 40 minutesInitiation of Synthesis and Mechanism- RNA Primaseo Makes RNA primer on DNA templateo Set of hybridized nucleotides- DNA Polymerase III o extends primer with DNA- DNA Polymerase I o removes RNA primer, replaces with DNA- continuous vs. discontinuouso continuous on the leading strando discontinuous on the lagging strand creates Okazaki fragmentso Antiparallel—DNA synthesized 5’3’ on both strands, creating the reason for leading and lagging strando Numerous replication forks simultaneouslyo Error rate of mispaired nucleotides 1 in 10^9-10^10 bases- Like an 8 million page book with no errorso Chromosome is about 1000 times longer than the cell- Why does the cell not continually initiate replication?o Can have multiple replication forks simultaneously Fast growing E. coli (generation time= 20 minutes) About 2.5 chromosomeso Controlling initiation DnaA doesn’t bind to hemimethylated DNA well- Bacteria will modify their DNAo Add a methyl group to adenosine of 5’-GATC-3’- Normally DNA fully (both strands) methylatedo Newly synthesized DNA is not—it is hemimethylates Partially methylatedo DnaA does not bind to this well Prevents constant initiation of
View Full Document
Unlocking...