The light chains also possess numerous V and J gene segments, but do not have D gene segments.

In the developing B cell, the first recombination event to occur is between one D and one J gene segment of the heavy chain locus.

Multiple copies of the V, D and J gene segments exist, and are tandemly arranged in the genomes of mammals.

RSS not associated with a V, D or J gene segment but participating in aberrant (illegitimate) V(D)J recombination are particularly difficult to recognize.

Seal S, Thompson D, Renwick A, et al.: Truncating mutations in the Fanconi anemia J gene BRIP1 are low-penetrance breast cancer susceptibility alleles.

They can avoid apoptosis by modifying the sequence of light chain V and J genes (components of the antigen receptor) so that it has a different specificity and may not recognize self antigens anymore.

In the bone marrow, each developing B cell will assemble an immunoglobulin variable region by randomly selecting and combining one V, one D and one J gene segment (or one V and one J segment in the light chain).