The new structure of the DNA has revealed that its shape is much more dynamic than what was historically explained by the famous “Watson-Crick” double helix model.
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DNA is made of about 3 billion base pairs, and can be spread up to a distance of 1 meter; this potential meter has to coil up inside a cell nucleus – so as you can imagine… it’s coiled up a lot. However, the shape of DNA isn’t always that straightforward. When longer segments of DNA are watched with a large-angle lens, the construction become exponentially extra complicated. Researchers reported in the journal Nature Communications those simulations showed that supercoiled DNA challenges commonly held idea of static DNA.
“When Watson and Crick described the DNA double helix, they were looking at a tiny part of a real genome, only about one turn of the double helix”, said Dr Sarah Harris of the University of Leeds in a statement.
The new structures were uploaded on a supercomputer and simulations were performed.
But the recent study analyzed several hundreds of base pairs, and the findings were surprising.
Researchers said that we need to better understand how DNA really looks like if we want to make advances in medical research.
To examine how the winding altered what the circles seemed like, the researchers coiled after which uncoiled the miniscule DNA circles – which is maybe 10 million occasions shorter in size than the DNA contained inside our cells – a single flip at a time.
Researchers basically wound and unwound tiny DNA circles just a single turn at a time, then devised a test to make sure they acted in the same way as full-length DNA strands.
They used an enzyme called “human topoisomerase II alpha” that manipulates the twist of DNA. The enzyme was shown to relieve the stress caused by all the winding, thus proving that the DNA in the circles appears and behaves like the longer DNA strands the enzyme encounters in human cells. First, scientists at Baylor made little circles of DNA and then used a microscopy technique known as cryo-electron tomography to create detailed images of them. The scientists have been astounded to check out that the illustrations is not the same as the prior unchanging dual curl DNA outline.
“Among the circles had sharp bends, a few had been determine-8s, and others seemed like handcuffs or racquets and even stitching needles”. The substance that they noticed was a wiggling, dynamic and morphing substance that constantly changed its shape.
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“The handsome double-helical structure we all know and love is not the actual active form of DNA”, said Dr. Lynn Zechiedrich, professor in the department of molecular virology and microbiology, and co-contributing author with Dr. Wah Chiu, professor in the Verna and Marrs McLean Department of Biochemistry and Molecular Biology.
