Question

Choose the incorrect statement with respect to dam and dcm genes?

(a) Their enzymes are responsible for methylation of DNA

(b) Dam protein methylates cytosine in –GATC-

(c) Dcm methylates cytosine in-CCAGG- and –CCTGG- sequences

(d) The extent of methylation also has effects on the efficiency with which the other restriction enzymes cleave the DNA in vitro

I had been asked this question in an internship interview.

My doubt is from Transformation and Hosts in portion Simple Cloning of Genetic Engineering

Answer 1

Correct choice is (b) Dam protein methylates cytosine in –GATC-

Explanation: The enzymes of dam and dcm genes are responsible for mrthylation of DNA. Dam protein methylates adenine in –GATC- and dcm methylates cytosine in –CCAGG- and –CCTGG- sequences. The extent of methylation also has effects on the efficiency with which the other restriction enzymes cleave DNA in vitro.