Biologists first took video of the process of doubling DNA

© James Graham, UC Davis // RIA Novosti / Alina Polyamide build process of individual DNA strandsBiologists first took video of the process of doubling DNA© James Graham, UC Davis // RIA Novosti / Alina Polyanina

. Scientists from the United States for the first time were able to obtain photos and videos of the process of doubling DNA of Escherichia coli, which turned out to be much more random than previously thought, biologists, published in the journal Cell.

«The speed of this process can change dramatically during Assembly of molecules dozens of times. It turned out that the proteins in the «Assembly line» DNA does not synchronized – everything happens by accident and they act completely independently from each other,» said Steven Kowalczykowski (Stephen Kowalczykowski) from the University of California, Davis (USA).

One of the distinguishing features of living organisms that separate them from viruses and inanimate nature, is their ability to create copies of its own genome, encoding all the components and processes occurring inside cells. This process, called DNA replication, is one of the most complex chemical reactions in the Universe.

In this process, as shown by the experiments of recent years, involved several dozen proteins, each of which performs different functions. First, chromosomes are «unwound» through the protein FACT, then the DNA «unravels» the enzyme of helicase, and then they are joined by protein-«anchor», primase and specific proteins, which scientists call DNA polymerases, start the copy process by reading the spiral and collecting the equivalent of a separate molecular «letters»-nucleotides.

The problem, as Kowalczykowski says, is that DNA consists of two spirals that polymerase, as initially suggested by scientists, copy at the same time. The first observation of the process showed that in fact one of them is copied more quickly than the other. The second polymerase from time to time «slows down», so that the molecules of proteins and their «servants» do not interfere with each other.

For this reason, many scientists believed that the work of polymerases in some way synchronized with each other, but the mechanism of this synchronization remained a mystery for them.

Kowalczykowski and his colleagues tried to find the answer to this question by tracing the copy short strands of DNA that the researchers extracted from E. coli and «glued» using a modified version of primase to the surface of the glass plate.

These plates biologists have placed in a solution where DNA polymerase, cellular «Energobalance» ATP and a specific set of nucleotides, marked with a glowing protein molecules. These proteins were shining only when attached thereto, the nucleotide was attached to a double strand DNA, which allowed the team Kowalczykowski to see how growing copies of the chromosome of Escherichia coli.

As it turned out, the secret work of the polymerases lies in the fact that there is no synchronization between them – the process of replication of both strands were completely random. When you see the «conflicts» between the collectors of the DNA the process of lengthening thread just essentially started anew.

The opening of this random mechanism, as scientists believe, will help us to understand how errors occur when copying the DNA and figure out how particularly polymerases affect the speed of evolution and mutation accumulation.

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