The process of assembling the DNA sequences that encode an immunoglobulin or a T-cell receptor (TCR), the cell-surface protein that recognises an antigen. The process excises polynucleotide sequences between V (variable), D (diversity) and J (joining) sequences, with the assembly of a coding sequence that will encode a complete potential immunoglobulin or TCR. The mechanism involves excision at recombination signal sequences (RSSs) that are characterised at each end of the to-be-excised sequence by 23 and 12 bp sequences (the 12/23 rule) that will be fused together in the signal joint as the excised sequence is cyclized. The ends of the coding sequences, which were sealed as hairpin turns during the first phase of the splicing, are reopened, an overhang is filled in with the insertion of so-called P nucleotides, and ligated to form a coding joint.