DNA is the backbone of life and almost all of our planet depends on it but, on primordial Earth, a primitive version of its lesser-known sister – RNA – was the focal point for evolution, scientists have discovered.
RNA is structurally similar to DNA, except one of the four fundamental pieces, thymine, is substituted for uracil.
This changes the shape and structure of the molecule and scientists have long believed this chemical to be the cause of Earth’s first lifeforms.
An accidental discovery by Harvard academics has now found that a slightly different version of RNA may have been the key ingredient allowing for life on Earth to blossom.
Scientists claim that a chemical called inosine may have been present in place of guanine, allowing for life to develop.
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RNA is structurally similar to DNA, except one of the four fundamental pieces – thymine – is substituted for uracil. This changes the shape and structure of the molecule and scientists have long believed this chemical to be the cause of Earth’s first lifeforms (stock)
This slight change to the bases, known as a nucleotides, may provide the first known proof of the ‘RNA World Hypothesis’ – a theory which claims RNA was integral to primitive lifeforms.
Jack Szostak, a professor at Harvard University, along with first-author and graduate student Seohyun Kim, suggest RNA used inosine as a surrogate.
‘Our study suggests that the earliest 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),’ said Mr Kim.
Lab attempts to craft adenine and guanine, purine-based nucleotides that bond with thymine/uracil and cytosine, respectively in DNA/RNA failed when using what was available on primordial Earth.
Issues stemmed from the reaction producing to many undesirable side-products.
DNA is the backbone of life and almost all of our planet depends on it but, on primordial Earth (artist’s impression pictured), a primitive version of its lesser-known sister was the focal point, scientists have discovered. Inosine, not guanasine, enabled RNA to replicate with high speed and few errors, Harvard scientists claim
WHAT IS THE DIFFERENCE BETWEEN DNA AND RNA?
DNA – deoxyribonucleic acid – is widely known as the molecule found in the nucleus of all our cells that contains genetic information.
It is shaped like a double-helix and made of small sections called nucleotides.
Each nucleotide contains a nucleobase, a sugar, and a phosphate group.
The sugar component in this particular molecule is called deoxyribose and makes up the D in DNA.
This is a cyclic carbon-based chemical with five carbon atoms arranged as a pentagon.
At the second carbon atom there is an attached singular hydrogen atom in deoxyribose.
This can also have an additional oxygen attached as well.
In this case, the oxygenated chemical then forms what is simply known as ribose – the R in RNA.
The deoxy prefix literally means without oxygen.
Shape of RNA and DNA
RIbose can do almost everything deoxyribose can and also codes for genetic information in some cells and organisms.
When the oxygen is present it drastically alters how the chemicals bonds and sits alongside other molecules.
When oxygen is present – in RNA – it can take a variety of shapes.
When oxygen is not present in this specific location – in DNA – the molecule forms as the iconic double helix.
Uses of RNA
DNA is often broken down into RNA and read by the cells in order to translate and transcribe the genetic code in order to make proteins and other molecules essential for life.
RNA uses three of the same base pairs as DNA: Cytosine, Guanine, Adenine.
The othe base pair, Thymine, is swapped out in RNA for Uracil.
RNA is also often found in simpler organisms, such as bacteria.
It is often also a virus, with Hepatitis, flu and HIV all forms of RNA.
All animal cells use DNA, with one notable exception: the mitochondria.
Mitochondrian are the powerhouses of the cell and turn glucose into pyruvate and then into Adenosine triphosphate (ATP) via the Krebs cycle.
This process is all done in this one organelle in the cells and ATP is the universal form of energy and used throughout every aerobic organism.
In the mitochondria there is a small strand of RNA which is unique in the animal kingdom.
It is passed down from the mother exclusively (the father’s lives in the sperm but is dissolved during fertilisation) and allows humans to trace their maternal lineage back throughout time.
Inosine enabled RNA to replicate with high speed and few errors, a feature which is essential for reproduction.
Researchers said: ‘[It] 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.’
Professor Szostak and Mr Kim’s discovery could help substantiate the RNA world hypothesis. In time, their work might confirm RNA’s primary role in our origin story.
Eventually, armed with this knowledge, scientists may be able to identify other planets that have the essential ingredients and determine whether we share this universe or are, indeed, alone.
The research was published in the journal Proceedings of the National Academy of Sciences.