Explain briefly how a vast number of immunoglobulins of different antigen specificities can be produced from the relatively small number of immunoglobulin genes present in the genome. Include the following terms in your explanation: somatic recombination;

Question

What will be an ideal response?

Answer 1

In developing B cells, gene rearrangements within the genetic loci for immunoglobulin light and heavy chains can produce an almost unlimited variety of different variable regions, and thus produce the huge repertoire of antibodies with different specificities for many types of antigen. This gene rearrangement mechanism is called somatic recombination. In the germline configuration, before gene rearrangement, the immunoglobulin loci in progenitor B cells are composed of sequences encoding the constant regions and families of gene segments encoding different portions of the variable region. Heavy-chain loci contain a series of gene segments called variable (V), diversity (D), and joining (J). Light-chain loci contain only V and J gene segments. In somatic recombination in developing B cells, one of each family of gene segments is randomly selected and joined together to give a complete variable-region sequence, which is subsequently expressed as an immunoglobulin heavy or light chain. Immunoglobulin gene rearrangement is irreversible, leading to permanent alteration of the chromosome; it occurs exclusively in B cells.