Distribution of "minor" nicks in bacteriophage T5 DNA.

Bacteriophage T5 DNA can be released from the phage particle in such a way that one end of 5 to 10% of the DNA molecules remains attached to either the phage head or tail. Under partial denaturation conditions, the DNA preferentially denatures in the vicinity of a nick so that the nicks can be located relative to the end that remains attached to the phage head or tail. Two classes of nicks were found. "Major" nicks were those found in more than 20% of the molecules and were located at the same points along the DNA molecule as reported by others. "Minor" nicks were found in 5 to 10% of the molecules and often occurred at specific locations near a "major" nick.