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thousand of these nucleotides form a gene, the smallest unit of complete information. The gene, when it encounters a gene from another parent, will combine with it in a certain way, and hence it carries certain information. And that is what inheritance is. There is nothing unique about human genetics in this respect. You're the product of a bunch of nucleotides coming together and combining in a certain way, and so is a lentil!"
The trick is to get down to the DNA. There are no less than two meters of DNA in a cell. Incredibly, once treated, it can be seen with the naked eye--"like long, thin strands of cotton," says Mr. Eujayl. But it is extremely fine; in the case of lentil, it weighs 4.2 picograms, a picogram being 10-12 of a gram. The researcher can hardly string it out with tweezers. However, it is negatively charged; so s/he exposes it to a positive charge, and it will then stretch itself in the direction of the positive charge. The next step is to stain it with a dye that interacts with DNA so that the latter may be seen under ultraviolet light.
Those genes will be strung together in a certain order to make the hybrid chromosome. "If we can look at the chromosome and find a pattern of genetic markers which segregates in the same manner as the trait--cold tolerance, for
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example," explains Mr. Eujayl. Then we hit the region where the gene(s) controlling that trait is/are located.
"And then we're there. We can compare the genetic makeups of plants which share known characteristics and see which patterns occur where in the progenies. We have then identified the linkage between the DNA marker pattern and the trait--in this case, resistance to vascular wilt, or cold tolerance. Henceforth, if we want to know whether a wild relative someone has collected in the wilds of Turkey has the traits we're looking
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of time in plant breeding."
The technique of breaking down the cell was pioneered in the mid-1980s; gene mapping has now been going on for several years, at ICARDA and a number of institutions worldwide. What is exciting about Imad Eujayl's work is the large number of markers mapped--254, making it by far the most comprehensive lentil gene map so far. Moreover the study was done with lentil population which had been bred to the eighth generation, giving an exceptionally stable genetic composition.
"We can then use the tool [the linked marker] on lentil sent to us by cooperating national programs, say Sudan, Iran or Argentina--and we can tell them where they can find the genes for what they may be lacking, for example, wilt resistance. They can then cross the relevant parents, which we may well be able to supply. This will save years, and a lot of money, in lentil breeding.
"This, to me, is what biotechnology is all about. We need to apply this technique to more and more crops. But we also need to demystify the process. It is neither magical nor sinister. In this case, it's just an analytical tool. Anyway, biotechnology is like any science or engineering product--including the automobile; it's as safe or as dangerous as the people who use it."
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