Once again about the benefits of garbage
Doubling of "junk" DNA turned monkeys into humans, scientists say
The ancestors of humans could gain intelligence and take the first steps to create tools due to the doubling of the so-called junk DNA, which happened about three million years ago, scientists said at a meeting of the American Society of Human Genetics.
"These sites are interesting because they enhance the activity of not only neighboring genes, but also other segments of the genome. In other words, doubling the same "junk" DNA can affect the work of several genes at once, which will enhance its effect on the body. We can say that our discovery for the first time allows us to seriously think about what makes a person human and what distinguishes us from primates," says Megan Dennis from the University of California at Davis (in a press release of the American Society of Human Genetics Duplications of Noncoding DNA May Have Affected Evolution of Human-Specific Traits – VM).
The genomes of humans and chimpanzees coincide by 99%, but our nervous systems develop completely differently and suffer from different problems in old age. These differences prevent scientists from using primates to study various diseases and how humans acquired the ability to speak and think intelligibly.
In recent years, scientists have discovered several hundred genes responsible for brain development and differing in structure in the genomes of humans and chimpanzees. However, they were never able to find those sections of DNA that were responsible for the unusually large, compared to the rest of the body, the size of our brain. Therefore, neurophysiologists and geneticists have long suspected that the reason for the striking difference between the two species lies not so much in the structure of genes as in their different activity.
Two years ago, scientists found the first practical confirmation of this hypothesis by transplanting part of the sections of "junk" human DNA that controls the activity of neighboring genes into the genome of a mouse embryo. This procedure significantly increased the size of the embryo's brain, but scientists were unable to follow its further development, as the experiment was discontinued for ethical reasons.
Dennis and her colleagues once again confirmed this hypothesis and discovered several new sections of "junk" DNA associated with the development of typically human brain traits. They studied rather long sections of this DNA, repeated several times in the human genome, but absent in the genetic material of primates or other animals.
Many of these sequences, as Dennis notes, are almost completely identical to each other, which is why scientists used to consider them sequencing errors and simply deleted them from the data.
It turned out that they played an important role in the work of the human genome and in what distinguishes humans and primates. In total, geneticists managed to discover about two hundred similar repetitive sites that somehow influenced the development of the human brain.
For example, transplantation of the "junk" DNA surrounding the SRGAP2C gene, the "conductor" of neuronal growth, significantly increased the size of the prefrontal cortex and increased the number of connections between its neurons in the brain of the mouse embryo. This gene and the associated "junk" DNA appeared about three million years ago, when people began to master tools and become upright.
Now geneticists are studying the work of other doubled sites, but the information already available, according to Dennis, is enough to say that the appearance of additional copies of "junk" DNA was a key step in human evolution, forever separating us from other primates.
Portal "Eternal youth" http://vechnayamolodost.ru