The dominance ofexrBoverexrB+in heterodiploids ofEscherichia coli

Abstract

SUMMARYTo test whetherexrB, a mutation inEscherichia coliB making this strain sensitive to ultraviolet radiation and unable to divide normally, is dominant toexrB+, merodiploids were constructed by crossing HfrexrB metA+his× F−malB met A thr proA recA. metA+recombinants were fertile (F′) and sensitive to UV. One of these, F′exrB proA, was crossed with an F−metA malB thr, selecting formetA+proA+. All such progeny acquiringmalB+were UV-sensitive, fertile and segregatedmet malUV-resistant progeny. They were, therefore, meriodiploids, F′exrB/exrB+.exrBis dominant toexrB+, in which respect it resemblesexrA(lex).