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?

Question

Quizplus · Accepted Answer

In mismatch repair-defective strains, A:C and G:T mispairings are not efficiently repaired, leading to A-to-G and T-to-C transitions being more common among spontaneous mutations.