Today all known organisms use the same genetic molecules to store information, known as nucleic acids. There are two types of nucleic acid: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). What kind of genetic information vector opens up life on Earth, DNA or RNA? Scientists have been arguing about this for a long time. A study recently published in the leading academic journal Nature has for the first time showed that at the beginning of life, there may be both, with certain basic components of DNA and RNA forming and co-existing in the Earth’s “primitive soup” at the same time.
The work by the Molecular Biology Laboratory (LMB) of the Cambridge Medical Research Council (MRC) challenges the mainstream hypothesis about the origin of life, the “RNA world” theory, which originated in the 1960s and was widely accepted.
Genes are written by DNA, which transcribes information into RNA, which carries instructions for making proteins. The “WORLD OF RNA” theory holds that life begins with RNA molecules: it can both store instructions and operate like a simple machine, giving it the potential for self-replication. The theory is that, as evolution, life in the RNA world has given way to the age of DNA and protein, because DNA is more stable and durable than RNA.
In the new study, the researchers simulated the conditions of shallow pools on the earth on primitive rocks. They dissolve RNA-forming chemicals in water, then dry and heat them, then simulate early solar radiation to expose them to ultraviolet light.
In this re-enactment of early geochemistry, the intermediates that synthesize the two basic components of RNA are also converted into two basic components of DNA. Specifically, the four basic components of nucleic acids can be produced from the same conditions and reactants: cytosine (cytidine, C) and ureaside (uridine, U), which are components of both RNAs, and deoxyadenosine, dA, which are components of DNA. The dna adenosine part is converted into deoxyinosine (deoxyinosine, dI), another component of DNA.
Experiments to simulate early geochemistry produced 2 RNA components and 2 DNA components
“It is critical that two DNA nucleosides can form base pairs with U and C.” “As a result, U, C, dA and dI form a complete genetic alphabet,” the review in Nature states. “It could also have been the original genetic alphabet on the original earth.
“The RNA world hypothesis holds that life begins with RNA and then comes with genetic substitutions — including primitive biosynthesis mechanisms and natural selection — that result in DNA.” Professor John Sutherland, the scientist who led the work, said: “Our work shows that, consistent with the primitive shallow pool, genetic systems that mix RNA and DNA essentialcomponents coexist at dawn of life. To allow life to appear spontaneously on Earth satisfies a premise that many consider critical. “
The researchers believe that these four components coexisted before life evolved, the beginning of the original genetic alphabet. Professor Sutherland added: “The nucleic acids – RNA and DNA – are linked to each other, and this work suggests that they are differentiated from one hybrid ancestor, not from one to the other.” “
“Genetic information always goes from nucleic acids to proteins rather than vice versa, which is called the ‘central law’ of molecular biology. So what we need to do now is figure out how the information that nucleic acids store and transmit is used to make proteins in the first. “
Understanding the chemical origin of life is the foundation of natural science and can enlighten future synthetic biology design. Dr Megan Dowie, head of the MOLECULAR and cell medicine department at MRC, commented, “This study shows that the so-called ‘blue sky study’ that cannot be immediately applied reveals fascinating insights at the beginning of life and demonstrates the importance of supporting basic research.” Such fundamental discoveries in life sciences will make it possible to make exciting future strategies for human biology. “