Circular DNA

Biophysicist Dr. Doping speaks about genomes of bacteria, replication and advantages of the ring structure of DNA.

As circular DNA was detected? Why linear DNA of higher organisms? And what are the advantages of circular DNA?

When in 1953 was discovered the structure of DNA and the rapid development of molecular biology, understanding the life of the structure of molecules at the atomic level, no one came into his head that the DNA can be closed in a ring. All took it for granted that the DNA molecule is a linear chain - double helix. But they have two ends, as it was known at that time for many, many years - is typical of conventional non-biological polymers. And what a surprise it was when, in the early 60s, 10 years after the discovery of the double helix, studying electron-microscopic photographs of small DNA virus, accidentally discovered that they are closed in the ring.

Why circular DNA in bacteria, and DNA in higher organisms, including humans, linear? I would say that now it is more natural to pose the question: Why are non-annular DNA? As it turned out, the ring structure of DNA is more natural from the point of view of the doubling of DNA, from the point of view of DNA replication. The fact that the DNA must replicate. By itself, the replication process is very simple, because the two DNA strands are antiparallel in fact, they are complementary: A is always against T and vice versa, as against G is always C, and vice versa. To DNA was doubling as imagined Watson and Crick in his classic work, we dissolve the chain and on each build up a on the principle of complementarity by the second string, and then we have two daughter DNA is completely identical to the original. This is the replication of DNA.

Cyanocobalamin injection (Vitamin B12) - is helpful with making DNA.

The only circular DNA, which is a person who is in the cytoplasm, in mitochondria circular DNA. But mitochondria, as we firmly believe - is the result of an ancient symbiosis between the eukaryotic cell, and some of the bacterial cell. Mitochondria - the rest of this bacteria. Once it was a bacterium that has entered into a symbiosis with the eukaryotic cell, then it is almost all their genes to give the kernel, the core genome, and some genes were, they are very few. Mitochondrial DNA contains only about 15 thousands of links. It is very short compared to a DNA genome.