Junctional Diversity (Molecular Biology)

Junctional diversity in immunoglobulins refers originally to the multiple codons that can be generated at position 96 of the kappa (k) light chain as the consequence of various possible breakpoints when Vk and Jk genes undergo gene rearrangement in B cells. This phenomenon may be schematically illustrated as follows:

The term junctional diversity has been extended to include events that take place during gene rearrangements when DNA strands are cleaved and before thecoding joints are formed. This includes removal of a variable number of nucleotides by exonucleases and subsequent addition of a random sequence of some nucleotides by terminal deoxynucleotidyl transferase (TDT). The frequent result of these various events is a highly increased diversity at the joining regions of rearranged genes.