In E.coli,the adenine in the sequence GATC is methylated by the Dam enzyme.In the same cells a restriction endonuclease recognizes and cleaves dsDNA with GATC on either strand.Why does E.coli have these two enzymes?
A) The enzymes cut the E. coli genome into pieces that bind to viral particles and inhibit viral replication.
B) The enzymes increase the rate of mutation and genome rearrangement, thus increasing the likelihood that E. coli cells will mutate and become resistant to viral infection.
C) The enzymes encourage lysogeny because the cleavage sites are recognized by viral integrases.
D) The enzymes protect E. coli from infection by preferentially degrading viral or other exogenous DNA that is not methylated.

Question

Quizplus · Accepted Answer

The Dam enzyme methylates the adenine in the GATC sequence to protect the E.coli genome from being degraded by its own restriction endonucleases. This is because the restriction enzyme recognizes and cleaves unmethylated sites, which are not present in the host genome but may be present in exogenous DNA, such as viral DNA. Therefore, the two enzymes work together to protect E.coli from infection by preferentially degrading viral or other exogenous DNA that is not methylated.

In Ecoli,the Adenine in the Sequence GATC Is Methylated by the the Dam