Module 1: E. coli and DNA Polymerase 1 Flashcards
What is the stoichiometric composition of bases:deoxyribose:phosphate in DNA
1:1:1
What did Avery and colleagues show?
The ‘transforming principle’: DNA from virulent bacteria could convert avirulent bacteria to be pathogenic
What two discoveries did Chargaff find?
1) Base composition varies between species and 2) the number of A & T bases are equal and the number of G & C bases are equal
What did the Hershey and Chase experiments show?
That DNA was the genetic material: viruses with 32P labeled DNA and 35S labeled protein were made. Only the 32P made it into the infected cell.
What type of replication occurs in living systems?
Semi-conservative replication
How did Messelson and Stahl show replcation was semi-conservative?
By labeling diving E. coli with heavy N. After two rounds of replication they saw that half the DNA was heavy and half was light; means replication is semi-conservative
What did Aruthur Kornberg discover?
DNA Polymerase I
What 4 characteristics did Aurthur Kornberg discover about DNA Polymerase I?
1) Adds nts using a template 2) Requires a primer to start synthesis 3) adds nts in the 5’ –> 3’ direction 4) Has the ability to proofread
What are the two substrates of DNA Polymerase I
1) Template primer 2) Activated dNTP
T/F: DNA Polymerase can initiate DNA synthesis de novo
False; DNA synthesis requires an RNA primer
The elongation of DNA is a reversible reaction. Why does this not occur in vivo?
The enzyme pyrophosphotase cleaves pyrophosphate into two phosphate ions preventing the reverse reaction
What types of DNA can Pol I bind? (3)
1) ds circular DNA that is nicked 2) the termini of linear DNA 3) ssDNA
T/F: DNA Polymerase I binds DNA in a sequence-specific manner
False: DNA binding is not sequence-specific
What catalytic activities does Pol I possess?
Polymerase, 3’–>5’ exonuclease, and 5’–> 3’ exonuclease
What catalytic activity does a Klenow fragment possess?
3’ –> 5’ exonuclease
