Comparison of the Physical Maps and Redundant Ends of thre Chromosomes of Phages 2C, SP01, SP82 and φe

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Abstract
The physical map of 2C DNA (cf. following paper in thi9s journbal) was compared to the maps of SP01, SP82 and φe (Three other Bacillus Subtilis phages containing hydroxymethluracil in place of th ymine in their DNA). The overall organizatio9n of the four genomes was remarkab le similar, as indicated by the topology of Hae III and Sal I cleavage sements. The proof was gatheredfor ther pressence in the four phage DNAs of large redundant ends carerying a single Hae III recognition site. The location of the latter proved identical for 2C and SP01, but to two shifted in the DNAs of SP82 and φe. Since the redundant end components of these hydroxymethluracil genomes are colinear, as shown by cross‐hbridization studies, the shifting of the Hae III cleavage site is presumabley due to tow base substitutions, suppressing an endonulease recognition site and establishing a new site elsewhere. Relateddness between the genomes of this family of viruses was evaluated from the fraction of conserved restriction fragments. According to these calculation, 6% base substitutions have occurred within the four viral DNA, as shown by crosshybridization with restroiction fragments. These data indicate the occurrence of deletions, in addition to base subsitutions, as evolutionary mechanisms prevailing in the genomes of this family fo phages.

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