Structure of the replicating DNA from bacteriophage T4.

At an early stage of replication, parental T4 DNA shows a loop structure often displaying two 3'-ended, single-stranded "whiskers", located in trans configuration at the branching-points. Several such loops have been observed within a single T4 molecule. Occasionally, reinitiation occurred in the middle of a loop, which suggests that the loop was growing in both directions.