Biological Sciences: The Unexpected Location of a Gene conferring Abnormal Radiation Sensitivity on Phage T4

Abstract

THREE mutations have been characterized, each of which increases the radiation sensitivity of phage T4 by a factor of about two. The v gene, controlling excision repair, maps close to gene 1 which codes for hydroxymethyl-dCMP kinase, a precursor of phage DNA synthesis^1–3. The x gene, which probably is involved in a post-replication repair system, maps close to gene 43, the gene coding for the phage Kornberg polymerase^1,3,4. The third gene, y, affects radiation sensitivity in a similar manner to x⁵. It has not previously been mapped, although it has been shown to be unlinked both to v and to x⁴. We have now located the y gene on the circular genetic map of phage T4. Unlike v and x which as expected map close to known early genes involved in phage DNA synthesis, the y gene is surrounded by late genes which determine the structure and assembly of the phage head and tail (Fig. 1).