Basic components of the immune system part 19

Given this extraordinary ability to generate large numbers of antibody molecules, how does the immune system recognize all pathogen, including past, present and future? This diversity is achieved by the way in which the genetics of antibody production  is arranges. The light and heavy chains are carried on different chromosome. The heavy chains genes are carried  on chromosome 14. These genes are broken up into coding systems called exons with intervening segments of silent segments called entrons. The exons represent the central region of the heavy chain and a large number of V regions. Between V and D genes are two small sets of exons called  the D and J. With each singleB  cell, one V gene is joined to one D and J in the chromosome.The product, The VH domain, is then joined at the level of RNA processing to Cu and B cell makes  an IgM molecule. By omitting the CU gene and joining VHDJ to a Cλ an IgG molecule is produced. This enormous versality allows the cell to make IgM, IgD, Ig G, IgA or igE in sequence while using the same variable regions. The heavy chain  gene recombination activity genes called RAG1 and RAG2. If these genes are eliminated by "knock out" techniques in mice, profound immunodefisiency status occurs in these animals, characterized by absent nature B and T cells