MARKER-DEPENDENT RECOMBINATION IN T4 BACTERIOPHAGE. II. THE EVALUATION OF MISMATCH REPAIRABILITIES IN CROSSES WITHIN INDICATOR DISTANCES

V. P. Shcherbakov ¹, L. A. Plugina ¹, E. A. Kudryashova ¹, O. I. Efremova ¹, S. T. Sizova ¹, and Oleg G. Toompuu ²

¹ Institute of Chemical Physics, Academy of Sciences of the U.S.S.R., Chernogolovka 142432, Moscow Region, U.S.S.R.
² Institute of Experimental Biology, Academy of Sciences of the Estonian S.S.R., Harku 203051, Estonia, U.S.S.R.

The contribution of mismatch repair to genetic recombination in T4 phage has been evaluated by three independent approaches: (1) testing for non-additivity of recombinant frequencies; (2) measurements of double exchange frequencies in three-factor crosses: (3) comparisons of recombination abilities of mutations occupying the same site. Quantitative agreement among the results of these approaches suggests that within distances much less than the mean length of hybrid regions, mismatch repair accounts perfectly for high negative interference as measured in three-factor crosses and as manifested by non-additivity in two-factor crosses. The mismatch repair mechanism readily recognizes only particular mismatches, the repair frequency being dependent on the base sequence in both strands of the mismatched region.