Which of the following statements is true regarding kappa, lambda and heavy chain immunogloblins ?
Coded in the same site of a chromosome
Coded in different sites of same chromosome
The chains are formed by genetic rearrangement after maturation
All
Ans. is 'c' i.e., The chains are formed by genetic rearrangement after maturation Genetic rearrangement of antibody . During B cell development, diversity of the antigen binding variable region of Ig is generated by an ordered set of Ig gene rearrangement. . An antibody is composed of two identical light and two identical heavy chains, and the genes specifying them are found in the 'V' ( variable ) region and the 'C' ( constant ) region. . As the name suggests, genetic rearrangement occurs in variable region , constant region remains constant, i.e. there is no rearrangement at constant region. In the heavy chain, 'V' region there are three segments ; 'V', 'D' and . For heavy chain, there is first a rearrangement of D segment to J segment, followed by a second rearrangement between a V gene segment and the newly formed D-J sequence; the C segment is aligned to the V-D-J complex to yield a functional Ig heavy chain gene (V-D-J-C). . Similar rearrangements occur for light chain V- region except there are only two segments involved; 'V' and %Y. . Light chain rearrangement occurs during later stages. A functional K or X chain is generated by rearrangement of 'V' segment to J segment, ultimately yielding an intact Ig molecule composed of heavy and light chain.