Which of the following occurs in the chromosome by the action of restriction enzymes?: (A) tRNA restriction, (B) DNA restriction, (C) mRNA restriction, (D) rRNA restriction
Answer is B. Restriction enzymes (restriction endonucleases) provide bacteria with a mechanism to distinguish between their own DNA and DNA from other biologic sources. These enzymes hydrolyze DNA at restriction sites determined by specific DNA sequences ranging from 4 to 13 bases. Each bacterial strain that possesses a restriction system is able to disguise these recognition sites in its own DNA by modifying them through methylation of adenine or cytosine residues within the site. Ref: Weil P. (2011). Chapter 39. Molecular Genetics, Recombinant DNA, & Genomic Technology. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.