According to recent scientific research published in Proceedings of the National Academy of Sciences, a primitive version of DNA’s sister molecule, RNA, was where evolution of life began billions of years ago.
RNA is like DNA, except it doesn’t come in the iconic double-helix shape. It is still structurally similar, despite the fact that one of its four fundamental molecules, thymine, is replaced by uracil. Scientists have long believed that RNA was the key for life to begin flourishing on Earth.
But a discovery made by accident by Harvard researchers suggests this flourishing was caused by a slightly different make-up of the RNA molecule. Specifically, they believe that inosine may have replaced guanine in the RNA, which would have facilitated the development of lifeforms.
The change to the base nucleotides that make up DNA and RNA is the first possible evidence we have supporting the “RNA World Hypothesis,” which posits that RNA was essential to the development of the most primitive microbes.
Inosine was a surrogate for the RNA, according to Harvard University’s Professor Jack Szostak and graduate student Seohyun Kim. “Our study suggests that the earliest life forms of life (with A, U, C, and I) may have arisen from a different set of nucleobases than those found in modern life (A, U, C, and G),” Kim said.
When attempts were made in the laboratory to recreate adenine and guanine in DNA and RNA with the materials believed to have existed on primordial Earth, they failed. The nucleotides adenine and guanine are based on purine and bond with thymine/uracil and cytosine, respectively.
Too many undesired by-products were produced in the chemical reaction, causing issues. With inosine, however, the RNA was able to replicate quickly and with few errors, which are characteristics necessary for reproduction of the molecule to take place.
According to the research, this “turns out to exhibit reasonable rates and fidelities in RNA copying reactions. We propose that inosine could have served as a surrogate for guanosine in the early emergence of life.”
This discovery could substantiate the RNA World Hypothesis, in time possibly confirming RNA’s role in explaining where we came from.
In addition, this could help scientists identify which other planets have the essential components needed for life to exist.