In E. coli, the dam gene encodes a methylase that enzymatically adds a methyl group to adenines. In dam- mutants, this methylase activity is missing and adenines remain unmethylated. How do you think the absence of methylase activity affects the rate of spontaneous mutation in these mutants?
DNA methylation is a posttranslational modification occur in E.coli due to dam gene which encode a special enzyme known as methylase
d = DNA
a=adenine
m=methylase
Through this process a methyl group bind to adenine, which help in a number of physiological process in the E. coli and also assist in the prevention of mutation and activate DNA repair pathway in the cell. When this gene is halted or absent completely then methylase enzymatic activity also nullify and as result there would not be DNA methylation through this process that make DNA vulnerable to the spontaneous mutation and DNA repair as well as replication pathway also compromised and there are fair chance to have mismatch during replication in such scenario.
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