The DNA code is a natural example of a large data file. Mutations and natural selection keep on editing this file - many files, in fact. Usually it was assumed that we inherit the file from our parents only (plus some mutations). If a piece of the DNA code of both parents is damaged, then the son or daughter has bad luck. There's no way to fix it.
Or is there?
David Goss has pointed out a new fascinating discovery in genetics described in the New York Times:
The biologists at Purdue University have found that 10 percent of off-spring of a plant are able to repair a genetic problem of both parents. The only acceptable explanation that the biologists have been able to propose is the following:
- The organisms carry not only the parents' code, but also a cryptic backup of the code from the grandparents (and maybe beyond). This code is sometimes used if something goes wrong with the parents' code.
Let me philosophize a bit. If you remember your biology classes, you know that there are dominant and recessive genes. Recessive genes are those that are inconsequential in a heterozygous genotype (i.e. in which there are two copies of an allele that differ). My countrymate Gregor Mendel, the father of genetics, has described many examples of recessive genes of a plant. But I guess that he would have assumed that if both parents have an important segment of the DNA damaged, it can't get fixed. But it can.
I feel that it is morally right to say that the backup of the critical DNA code is analogous, if not an example, of a recessive gene. More philosophically: if Nature can do something that we can, be sure that it's possible that it has been able to develop this technology after those billions years of attempts - and only an experiment can show whether it has actually developed it. Nature is wicked smart, and DNA code backup may be another example.
The stored data do not seem to be in the form of DNA - a copy of the same sequence does not seem to appear in the DNA strand. The second most likely explanation is then RNA - it's less stable than DNA and it was assumed that it can never be used as a primary source of the genetic information. Well, maybe it can, at least in the extreme cases.
It is not know whether the same phenomenon may be observed for other types of organisms. If it is so, a popular theory designed to explain the existence of sexes - namely as a tool to avoid excess mutation - could be in trouble because the DNA backup could be far more efficient in doing the same job.
