Gene drive in mammals
Scientists have inserted "self-replicating" genes into mammalian DNA for the first time
Geneticists from the United States have for the first time built into the DNA of mice a special set of "self-reproducing" genes, which allows you to quickly distribute certain gene variations throughout the animal population, according to an article posted in the electronic library bioRxiv.org (Grunwald et al., Super-Mendelian inheritance mediated by CRISPR/Cas9 in the female mouse germline).
"This work confirms that such techniques can really work for mammals, but at the same time it sobers us. We still have a lot to do in order to turn such genes into a tool for controlling rodents or other pests," comments Paul Thomas, a geneticist from the University of Adelaide (Australia), whose words are quoted by the journal Nature.
Gene Wars
The CRISPR/Cas9 genomic editor, called the main scientific breakthrough of 2015, was discovered by American scientist Feng Zhang and a number of other molecular biologists about five years ago. Since then, it has undergone several upgrades that allow scientists to use it to edit the genome with one hundred percent accuracy.
Almost immediately after the discovery of this system in the DNA of bacteria, scientists began to think about whether it could be used to distribute the "necessary" versions of genes very quickly and reliably across populations of various living beings.
The fact is that CRISPR/Cas9 and other DNA editors can be inserted into the genomes of unicellular creatures or even multicellular animals in such a way that they will begin to delete all the "wrong" copies of genes and replace them with the "right" DNA sequences in all its cells.
As a result, all the offspring of genetically modified and "normal" living beings will always be carriers of the "correct" copy of the gene, and not only in half of the cases, as Mendel's laws say. Thanks to this, the "necessary" versions of genes will spread throughout the population in several generations, without requiring human intervention in the life of animals.
This can be used for a variety of purposes – the destruction of certain species of mosquitoes and midges that spread parasites, the protection of certain animal species from diseases or viruses, as well as a number of other purposes. Many scientists and politicians are extremely negative about this idea, as they believe that such "self-reproducing" genes cannot be controlled.
"Contagious" albinism
To date, as noted by Kimberly Cooper and her colleagues from the University of California at San Diego (USA), such "self-propagating" genes could be inserted only in DNA of yeast and insects. Her team took the first step towards implementing this controversial idea among mammals by experimenting with mice.
As a "target" for the insertion of the CRISPR/Cas9 system, scientists chose the Tyr gene, responsible for the synthesis of dark pigments in the body of all mammals, including humans. Damage to all its copies, as a rule, leads to the fact that the animal becomes an albino, so it is very easy to observe changes in its condition.
Having selected the correct "template" for the recognition of this gene by the Cas9 protein, the scientists "translated" it into the language of the cell, into a set of genetic "letters"- nucleotides, and inserted it into the DNA of several mice along with a set of instructions that forced the cell to synthesize Cas9 molecules. When the rodents grew up, biologists crossed them with several "ordinary" mice and checked what their offspring would look like.
As it turned out, the offspring of these rodents consisted of about 73% albinos. This simultaneously confirmed that "self-replicating" genes can also work in mammalian DNA, and showed that this procedure does not work as actively among them as among invertebrates. Such a technique, as the scientists themselves admit, cannot yet be used to combat rats and other four-legged "invaders" that were brought by Europeans to the tropical islands of the Pacific and Indian Ocean. On the other hand, it can already be used to raise animals predisposed to the development of complex genetic diseases.
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