Abstract
The DNA molecules of 4 temperate coliphages ([lambda], [PHI]80, 21 and 186) have deoxy-adenylate and deoxyguanylate at the 5[image]-termini of the 2 constituent strands. In DNA, deoxyguanylate is at the left end of the double-stranded molecule corresponding to the genetic marker susA, and deoxyadenylate is 5[image]-terminal at the other end. The more dense of the 2 strands of [lambda] DNA in alkaline CsCl with 5[image]-terminal deoxyguanylate is oriented with its 5[image]-terminus at the susA end.