Strains of E

Multiple Choice

Strains of E. coli that are defective in mismatch repair have very high levels of spontaneous mutagenesis. Studies have shown that in wild-type strains A:C and G:T mispairings (as opposed to the normal A:T and G:C pairings) that occur during DNA replication are more likely than other mispairings (A:G, etc.) to be detected and repaired in these mismatch repair-proficient, wild-type strains. Which of the following types of base substitutions would you expect to be most common among the spectrum of spontaneous mutations created by the mutant mismatch repair-defective strains?

A) A-to-C
B) C-to-A
C) G-to-C
D) A-to-G
E) A-to-T