The first living organism with three pairs of DNA bases

Bioengineers have added two new "letters" to the genetic code

Alexander Khramov, Infox.ru

For the first time, scientists were able to obtain a culture of living cells with six "letters" of DNA instead of four. Cells with a six-letter genetic code function in the same way as normal ones.

This is stated in an article by American scientists from the Scripps Research Institute A semi-synthetic organization with an expanded genetic alphabet, published in the latest issue of the journal Nature.

(The Scripps Research Institute Scientists Create First Living Organization that Transmits Added Letters in DNA 'Alphabet' can be read on the Institute's website – VM.)

As is known, the genetic information in the DNA of all living organisms on Earth is encoded by four nitrogenous bases ("letters") – adenine (A), thymine (T), guanine (G) and cytosine (C). A-T and G-C, located opposite each other, form hydrogen bonds, due to which the two strands of the DNA helix are connected.

The authors of the article synthesized two more nitrogenous bases that do not occur in nature – d5SICS and DNAm (you can read more about this in the article "Two new letters in the DNA alphabet" – BM). They also form hydrogen bridges between themselves and can be "sewn" into DNA strands. After a series of experiments in vitro, scientists inserted new "letters" into the ring chromosome of the bacterium Escherichia coli.

It turned out that cellular proteins responsible for replication (doubling) DNA before cell division, easily cope with the six-letter code. As a result, an E.coli culture with a modified genome can successfully reproduce. However, since d5SICS and DNAm are not produced in the cells themselves, scientists had to supply bacteria with a special transport protein that transports them from the external environment. If d5SICS and DNAm do not enter the cell at the time of replication, then the additional "letters" from the genome disappear.

Scientists do not exclude that in the future this technology will help to create organisms with fundamentally new properties. The fact is that the "letters" in DNA are read three at a time, and almost every triplet (for example, ACG) encodes only one amino acid. Accordingly, if you add two additional "letters", the number of possible combinations will increase dramatically. According to the researchers' calculations, a cell with a six-letter genome will be able to use up to 172 amino acids in protein synthesis, whereas only 20 are currently used.

Portal "Eternal youth" http://vechnayamolodost.ru 08.005.2014