(ORDO NEWS) — Under microgravity conditions, the level of copying errors in DNA increases markedly.
Mutations in DNA appear for a variety of reasons. For example, due to high-energy radiation that damages genetic letters – nitrogenous bases, which are part of DNA and which form the genetic code. Cosmic rays easily damage DNA, and it is not so easy to protect yourself from them completely: if we talk, for example, of the International Space Station (ISS), then despite all the protection, the level of radiation on it is about a hundred times higher than on Earth.
But cosmic radiation is not the only thing that can cause mutations in space. As you know, even without any mutagenic factors in DNA, errors appear at each copying – simply because copying enzymes (DNA polymerases) do not work with 100% accuracy. That is, when the daughter cells divide, some small differences from the mother cell will appear in the DNA.
It turns out that the accuracy of copying enzymes is influenced by gravity – at least it definitely affects bacterial DNA polymerase. Researchers from the University of Toronto and Queens University in Kingston performed an experiment in a Dassault Falcon 20 jet plane, which flew in a parabola: having gained an altitude of eight kilometers, it began a free fall, descending 3.3 km in 20 seconds.
Those on board felt weightlessness, or, more correctly, found themselves in microgravity. The experimenters had a special apparatus with them, in which, in a semi-automatic mode, it was possible to copy (replicate) a DNA fragment 1000 nucleotides long.
DNA was duplicated by E. coli DNA polymerase, and, according to an article in Frontiers in Cell and Developmental Biology, it made noticeably more mistakes under microgravity than under normal conditions. The percentage of mutations when the copying enzyme puts the wrong genetic letter in the DNA increased by 10-140%. Also, DNA polymerase sometimes completely forgot to insert a letter into the synthesized DNA chain, and sometimes, on the contrary, inserted one, two or three extra letters. True, DNA polymerases have a function for checking their own errors, and the largest number of mutations occurred when this function was turned off in the experimental polymerase.
Life evolved under the constant influence of the earth’s gravity, which, obviously, affected all levels of organization of living organisms, down to molecules. However, how exactly DNA copying machines sense gravity is not yet clear, and it is also not clear how dangerous it is for astronauts – after all, our cells and molecular processes are arranged in many ways differently from bacteria.
At the same time, everything may not be so scary: there are special repair services in the cells that correct mutations, and they do it so well that sperm cells that have been in orbit remain capable of fertilization and give rise to completely healthy embryos.
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