Explain how the mechanisms for immunoglobulin and T-cell receptor rearrangement may have evolved in humans

Question

What will be an ideal response?

Answer 1

It has been proposed that the evolution of rearranging antigen-receptor genes began with the insertion of a transposable element into a gene encoding an innate immune receptor. This gene was not only split into two segments, but also became flanked by repetitive DNA sequences donated by the transposon. A later chromosomal rearrangement event translocated the transposase genes to a different chromosome, where they evolved into the ancestral RAG-1 and RAG-2 genes. The repetitive DNA sequences left behind at the original receptor gene location evolved into the recombination signal sequences (RSSs), and the segments of the receptor gene evolved into V and J sequences. Eventually this led to a family of rearranging genes on five chromosomes encoding the immunoglobulin heavy- and light-chain genes, and the T-cell receptor ?, ?, ?, and ? genes.