How is the human genome able to encode billions of unique antibody molecules from only three gene sets? What will be an ideal response?

---

ANSWER: Humans can produce billions of different antibody molecules, each of which can bind to a
different antigen. Because there are billions of such combinations, it is impossible for each
antibody molecule to be encoded directly in the genome; there simply is not enough DNA in
the human genome to encode hundreds of millions or billions of antibodies.
Synthesis of a vast number of different antibodies is possible as a result of genetic
recombination in three clusters of antibody genes. These are the heavy-chain genes (H genes)
on chromosome 14 and two clusters of light-chain genes—L genes on chromosome 2 and L
genes on chromosome 22. These recombination events take place in B cell nuclei during
maturation, producing a unique gene in each B cell that produces one type of antibody. This
rearranged gene is stable and is passed on to all daughter B cells. This process of
recombination makes it possible to produce billions of possible antibody combinations from
only three gene sets.