1. Basel Institute for Immunology, Postfach, CH-4005 Basel 5, Switzerland
2. ^*Present address: MRC Laboratory of Molecular Biology, Hills Road, Cambridge, UK.

Abstract

DNA SEGMENTS coding for amino terminal and carboxyl terminal half of immunoglobulin chains are separate in the embryo, and specific rearrangement in these DNA segments occurs during differentiation of lymphocytes^1–3. Although the simplest model would be that the rearrangement brings a V gene in contiguity with a C gene, thereby allowing RNA polymerase to transcribe a whole immunoglobulin gene continuously, it has not been directly shown that this is really the case. One way to study this problem and which we report here is to hybridise DNA from a plasmacytoma with a purified light chain mRNA in conditions which would not permit renaturation of the gene segments, digest all single-stranded nucleic acid with single strand specific nuclease S₁ (ref. 4), and determine the size of the DNA segment which was protected by the mRNA from digestion with S₁ nuclease. Using the fact that the length of the immunoglobulin mRNA and its two regions corresponding to V and C genes are known with considerable accuracy^5,6, we have been able to determine that V and C genes are not contiguous.