Diversity and joining segments of mouse immunoglobulin heavy chain genes are closely linked and in the same orientation: implications for the joining mechanism.

We have mapped 12 diversity (D) gene segments of mouse Ig heavy chains between 80 and 1 kilobases 5' to the four joining (JH) gene segments by molecular analysis of DNA clones isolated from recombinant phage and cosmid libraries. All identified D and JH segments are in the same 5'-3' orientation. The significance of these findings with respect to the joining mechanism for Ig gene segments is discussed.