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Not a double helix, but a twisted knot: scientists first found a new form of DNA in human cells

Not a double helix, but a twisted knot: scientists first found a new form of DNA in human cellsPreviously, in some studies, the existence of DNA in an entangled form, designated as a “twisted knot”

Researchers from the Harvans Institute in Australia first found in living cells a new type of DNA structure – in the form of a twisted knot. The results of the research are published in the scientific publication Science Alert.

In 1953, scientists Rosalind Franklin, James Watson and Francis Crick first proposed the structure of a double helix DNA. Their discovery became the basis for modern molecular biology. Later, the model of the DNA structure proposed by the researchers was proved, and their work was marked by the Nobel Prize in medicine in 1962. It is through understanding the shape of the double helix DNA scientists were able to begin to unravel many of the secrets of the genetic code. But recently it became known that the double helix is ​​not the only form of DNA.

Earlier in some studies, the existence of DNA in an intricate form, designated as a “twisted knot”, was assumed. Scientists called it i-motif, but never fixed in living cells outside the test tube. Australian researchers found that such a structure in living organisms not only exists, but also quite common.

According to the description, the structure of i-motif is really similar to the “knot” of four threads. It is noted that these filaments are not connected in the same way as in the known double helix. The four types of nitrogenous bases (adenine, guanine, thymine, cytosine), which are usually denoted simply by the letters A, C, T and G, are stacked on top of each other in combinations: A – T, C – G. As scientists emphasize, this variation plays an important role in protein synthesis.

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In addition, researchers from the Garvan Institute developed an antibody that allowed “sniffing” i-motif in the genome and identifying them, labeling with immunofluorescent glow. This allowed scientists to see how often and where these DNA nodes appear. They found that i-motif can fold and unfold depending on the acidity of their surroundings and are a kind of switch that regulates gene expression.

The researchers will have to conduct several additional experiments to find out the functions of such nodes. So far, scientists have suggested that nodes can help enable or disable individual genes and affect whether the gene is actively read or not.

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