[en] Escherichia coli ruv gene was located at 36.1 min on the chromosome by P1 transduction experiments and the gene order his - supD - uvrC, dar4 - ruv - eda - fadD - pps was proposed. Complementation analysis by an F' factor carrying genes in the his region indicated that ultraviolet light sensitivity genes, ruv and uvrC, consist of different cistrons and wild-type alleles of these genes are dominant over the mutant alleles. (U.S.)