Modulation of mutation rates in bacteriophage T4 by a base-pair change a dozen nucleotides removed

Neighboring base-pairs are known to affect site-specific mutability. A previous analysis had suggested that such effects might decrease rapidly with distance. Here, however, we demonstrate a longer-range (unneighborly) base-pair effect on site-specific mutabilities: a single base-pair substitution substantially alters transition mutation rates at sites more than ten base-pairs away. DNA sequencing carried out during this analysis extends the known sequence of the rIIA cistron by 333 residues.