Practice question

Type II restriction-modification systems consist of separate endonuclease and methyltransferase enzymes recognizing identical sequences. The endonucleases typically recognize four to eight base pair palindromic sequences possessing twofold rotational symmetry and cleave phosphodiester bonds either within the palindrome or close to it, yielding defined blunt or sticky ends. Activity requires only magnesium ions as cofactor, independent of ATP or S-adenosylmethionine. Their precision, consistent fragmentation pattern, and ability to generate predictable termini make Type II enzymes indispensable tools for mapping, subcloning, genotyping, and recombinant DNA assembly in biotechnology.