V-geneone of a number of segments which encode part of the variable region of an IMMUNOGLOBULIN. These segments are clustered together in a specific region of the CHROMOSOME, away from the C-GENE which encodes the constant region of the immunoglobulin. During the development of a B-cell (see LYMPHOCYTE), a V-gene segment is selected and brought by gene rearrangement to a location just UPSTREAM of the C-gene to generate a functional ANTIBODY gene (see Fig. 315 ). For immunoglobulin light chain genes, a V segment joins at random to a J-GENE segment; for immunoglobulin heavy chain genes, a V segment joins to a D segment (see D-GENE). In this way the genetics of antibody diversity can be accommodated within the GENOME. see ENHANCER, PROMOTER.Enhancer activates promotor (p3), brought in with selected V segment (V3), for expression of the immunoglobulin light chain gene. V1 ,V2 ,V3 →Vn, V-gene segments. J1 -J5 ,J-gene segments.Note: At the heavy chain locus two rearrangements are involved in a similar manner t o the rearrangement to from the light chain gene.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005