DNA: much more than the molecule of life (I)

Changing the subject from my last post, it’s time to talk about DNA and the recent discoveries related to it. Let’s start with the most simple question.

What is DNA?

Deoxyribonucleic acid (DNA) is the biomolecule that encodes the genetic information of cellular organisms. It is composed of four molecules called nucleotides, which are represented with a letter: adenine (A), guanine (G), cytosine (C) and thymine (T). Moreover, two polymeric chains (DNA strands) connect these nucleotides, pairing them through hydrogen bonds. DNA strands roll themselves in a double helix. Each polymeric chain is composed of phosphate groups, chemically attached to riboses (sugars), and these in turn to the nucleotides. The latter always pair in the same way: A-T/G-C. Knowing this combination of letters, we can form any DNA chain. For example, if we have the next chain: ATTGCGTATG, we are able to guess the complementary one: TAACGCATAC. In addition, there is always a direction, a natural orientation, for each strand. Each one has a free 5′ phosphate group as well as a 3′ deoxyribose hydroxyl group.

The next short video (published by Plethrons) displays some more extra information about DNA, and about its storage. If you are interested in getting deep, you can also watch this video.

But I don’t want to make this introduction long. So let’s move to the updates in DNA.

Eight letters in a new DNA

A recent study published in Science, by Hoshika et. al1, has proved the existence of an 8-letters DNA double helix, without significantly modifying the features of the normal DNA. This discovery could give insight into other kinds of life. This new system has been named “hachimoji“, from hachi (eight) and moji (letters). The new nucleotides, named S, B, Z and P, also pair in a similar way S-B / Z-P.

Comparison between nucleotides and pairing of normal DNA and Hachimoji DNA.

These new nucleotides have increased information density over the common ATCG system, making them available for many other applications. Furthermore, the group of researchers has obtained not only DNA but also RNA. RNA (ribonucleic acid), unlike DNA, is usually a single-stranded polymer. Also, it contains uracil (U) instead of thymine (T). Among the main functions it takes part in, we can find coding, decoding, regulation, and expression of genes.

Back to the topic, this important discovery means a new life system potentially able to support molecular evolution (mutations, that are essential for evolution) or to even show evidence of new forms of extraterrestrial life. But you will probably wonder if you have these nucleotides in your DNA, or if you may have them in the future. The answer is NO, now you don’t. They are synthetic, that is, prepared in a lab. However, that could be the future and natural evolution of our current DNA.

  1. Hoshika et al., Science, 2019363, 884–887.

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