Name: Lauren A.
Susumu Tonegawa recevied the 1987 nobel prize for having
solved the problem of the genetic basis of antibody diversity. He
determined that this involved "somatic recombination of inherited gene
segments" what does this actually mean? In which cells does it occur? How
does the process (recombination) differ from cell to cell?
Visit the website www.nobel.se for a list of all Nobel
Laureates. I checked the press release for the Nobel
Prize of Medicine, 1987, where your question is
"In a pioneering study published in 1976 Tonegawa
could (...) show how parts of the genome of the cell
(DNA) is redistributed under its differentiation from
an embryonic cell to an antibody producing B
So the recombinations occur when embryonic cells
develop into B lymphocytes, and different
recombinations occur in each stem cell developing in a
new line of B lymphocytes. in this way a gigantic
repertoir of antibodies can be produced with a limited
number of genes. Check the complete story at
(note, that at that time the human genome was believed
to contain at least 100 000 genes in total. Now we
know that it is much less than that).
Simply put, (as I myself understand it!) it's kind of like having 3 decks of
cards and dealing out different combinations of a card from each deck. There
are 3 kinds of genes in antibody formation. They are V genes, J genes and D
genes. There are a certain number of V's, J's, and D's genes in our genome.
When a new antigen comes into the body new combinations of V's, D's and J's
are tried out until one can bind with the antigen. Recombining certain
numbers of existing genes takes up a lot less genome space than having a gene
for every antigen that could possibly come our way.
Lauren, let us break down the phrase. "Somatic" refers to specialized immune
system cells which produce antibodies as opposed to gametes. "Recombination"
refers to an editing and rearranging process. Prior to transcription,
sections of the "inherited gene" act like transposons, jumping genes, so that
they rearrange the coding exons. Frequently, only some of the exons or
"segments" are copied. Once transcription takes place, editing the immature
mRNA removes introns. Further rearranging of the existing exons sometimes
occurs here before translation takes place. Thus one inherited gene can give
rise to a multitude of slightly different antibodies which explains how such
a limited number of antibody coding genes can code for the more than 10-fold
increase in actual antibodies produced.
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Update: June 2012