Circular permutation analysis of phage T4 DNA by electron microscopy.

Phage T4 is known to have a linear duplex chromosome that is circularly permuted and terminally repeated. We found, by denaturation and self-reannealing experiments, that circular permutation in T4 native DNA is not random. Their multimodal distribution of permutation is compatible with the "headful packaging" model with the additional specifications that the encapsulation of DNA starts at several sites and these are not random distributed.