Where in the genome of living creatures genes come from that no any other types? New research shows that they often arise almost out of nothing, or rather of junk DNA.
All living organisms are in close relationship with each other. 30% of human genes are shared with E. coli and 50% with a banana. By the way, this is one of many proofs of the fact that all living things descended from a common ancestor.
However, each type has a small percentage of the genes unique only to him or his immediate family. In the genomes of other organisms no not only the exact copies of such DNA, but their obvious equivalents. Experts call them genes-orphans.
Where are these new in the evolutionary history of genes? There are at least two possible ways. First, the gradual accumulation of differences between related genes (divergence) can go so far that biologists simply do not identify “cousins”. It is believed that this scenario is most common for the occurrence of the genes of orphans.
There is another way. Recall that a gene is an instruction for the synthesis of RNA. RNA can serve as a prototype for protein synthesis (the main “workhorse” in the cell) or perform other functions.
But each genome has a mass of junk, or noncoding, DNA. This “former” genes which once completely out of order. They contained instructions for synthesis of RNA is unable to operate properly due to errors introduced by the mutations.
However, junk DNA continues to mutate. Moreover, these mutations are not “washed out” by natural selection, because non-coding DNA does not affect the life of the cell and organism as a whole (however, the latter thesis recently criticized). And sooner or later as a result of such accidental changes of this “garbage” may be a new functional gene. In this case, experts say that the gene originated de novo.
it is believed that this exotic scenario, which is rarely implemented. But a new study onpublished in the journal eLife, suggests something else.
Junk DNA turned out to be an important source of evolutionary change.Illustration of a CC0 Public Domain.
the Authors have developed a new technique allowing to determine whether the gene is an orphan working counterparts in the genomes of other species, even if the “cousins” did not like each other. Based on this method, scientists have searched for “lost relatives” for the genes of yeast, flies and humans.
the Results were discouraging.
“To our surprise, at most about one third of the genes of orphans are the result of divergence. This, in turn, suggests that most of the unique genes in those species that we investigated are the result of other processes, including the emergence of de novo. Consequently, it happens more often than scientists originally thought,” says co-author IFE of Maclise (Aoife McLysaght) from Trinity College Dublin.
Biologists did not stop there and asked the following question: what is the impact of the new genes on the human body?
as experimental organisms, researchers chose the yeast. They have short genomes, multiply rapidly and at the same time, belong to the eukaryotes, in contrast to, say, bacteria.
First, the researchers disabling genes are orphans, once resulting in yeast de novo. It usually did not reduce the viability of these organisms or “in vitro” or in natural populations. In other words, most of which appeared de novo genes are not essential (in any case, yeast). And this is the explanation: in the end, there was also a direct ancestor of yeast and without them.
In the second phase, biologists have gone the other way. On the contrary, they artificially increased the work (the expression of) the “newcomers”. And yeast immediately stepped growth. The specialists have verified that this reaction is not caused by the expression of some GEnew non-de novo.
in Other words, genes that have arisen “out of the garbage” can be very useful and give their bearers an important evolutionary advantages.
the Results of this study published in the journal Nature Communications.
Previously, “News.Science” (nauka.vesti.ru) wrote about the virus, the genome of which consists almost entirely of gene-orphans.