A strain of E.coli has been isolated that can’t correct any replication errors. It has a mutated ε subunit so that Pol III HE can still function as a polymerase but has lost its proofreading function as a 3’ to 5’ exonuclease. This E.coli strain also has a non-functioning mismatch repair system.
By considering the replication error rates in a wild type strain and the mutant strain, discuss the consequences of these mutations on the E. coli genome. To help with your discussion, think about the following questions:
• What is the normal replication error rate in E. coli?
• If you find an article that says something like an error rate is 5 x 10-2 errors per base pair, this means that 5 nucleotides every 100 base pairs is mutated.
• What is the base selection error rate of DNA pol III? That is, what is it’s rate of error when choosing which nucleotide to insert during DNA synthesis of replication?
• What is the genome size of E. coli?
• How many mutations would there be each generation of each E.coli strain?
• How many replications would it take for every nucleotide within the genome of the mutant strain to become mutated?
• Discuss the consequences of these mutations on the E. coli genome.
