(a) At the DNA level, one of the IGKV gene is joined to one of the 5 IGKJ genes, with deletion of the intermediary DNA, to create a rearranged IGKV-J gene. (b) The rearranged IGKV-J gene is transcribed with the IGKC gene into a IGKV-J-C premessenger RNA. (c) The RNA sequences corresponding to the introns and to the non-used IGKJ genes are excised by splicing, and a mature messenger which comprises the spliced coding regions, and the 5' and 3' untranslated sequences, is obtained. (d) The messenger RNA is translated into a polypeptide chain by the ribosomes. (e) The signal peptide is cleaved off by a peptidase following the entry of the polypeptide chain in the endoplasmic reticulum, and a mature kappa light chain is produced. L=L-PART1 (L: for Leader).