Two types of DNA rearrangements in immunoglobulin genes

Antibody genes, along with most other eukaryotic genes, are examples of "split genes. " One unique feature of the antibody-gene system is that it can rearrange indi-vidual gene segments by two distinct mechanisms dur-ing the differentiation f antibody-producing cells or B cells. These DNA rearrangements amplify the informa-tion encoded in the antibody-gene families. The antibody or immunoglobulin molecule is com-posed of two distinct polypeptides, light (L) and heavy (H) chains, both of which are divided into variable (V) regions responsible for antigen binding and constant (C) regions responsible for effector functions such as com-plement fixation. There are three unlinked families of antibody genes: two code for) ~ and x light chains, and the third codes for heavy chains. Light chains are en