Large double-Stranded DNA bacteriophages the T-even Phages T2, t4 and t6 T4(as example) 1.7X 105 base pairs Have a unique base, 5-hydroxymethylcytosine instead of cytosine The above hydroxyl group is modified by addition of glucosyl residues This glucosylated dna is resistant to virtually all restriction endonucleases of the hostLarge Double-Stranded DNA bacteriophages: the T-even Phages T2, T4 and T6 T4 (as example) – 1.7 X 105 base pairs – Have a unique base, 5-hydroxymethylcytosine instead of cytosine – The above hydroxyl group is modified by addition of glucosyl residues – This glucosylated DNA is resistant to virtually all restriction endonucleases of the host