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Name: Lauren A.
Status: Student
Age: 19
Location: N/A
Country: N/A
Date: N/A 


Question:
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?



Replies:
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 answered:

"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 lymphocyte."

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

http://www.nobel.se/medicine/laureates/1987/press.html

(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).

Trudy Wassenaar


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.

vanhoeck


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.

Cherie Breffeilh



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