Discovery Strengthens the Theory that Life on Earth Born from an RNA-DNA Mix

Chemists have made a discovery that supports a surprising new view of how life originated on our planet.

applied Chemistry In a study published in the chemistry journal, they showed that a simple compound called diamidophosphate (DAP), which existed reasonably on Earth before life emerged, could chemically combine tiny DNA building blocks called deoxynucleosides into primitive DNA chains.

The finding is the latest in a series of discoveries in the past few years, where DNA and its close chemical cousin RNA emerged together as products of similar chemical reactions, and the first self-replicating molecules and the first life forms on earth were mixtures of the two.

Discovery could also lead to new practical applications in chemistry and biology, but its main significance is that it addresses the age-old question of how life on Earth first originated. In particular, it paves the way for more comprehensive studies of how self-replicating DNA-RNA mixtures may have evolved and spread to the primitive Earth and ultimately seeded the more mature biology of çağıl organisms.

“This finding is an important step towards the development of a detailed chemical model of how early life forms appeared on Earth,” says Ramanarayanan Krishnamurthy, an associate chemist at Scripps Research.

The finding also indicates the area of ​​origin of life, chemistry, Set’in It takes away from the hypothesis that it özgü dominated over the last decade: The “RNA World” hypothesis suggests that the first replicators were based on RNA, and that DNA emerged only later as a product of RNA life forms.

Is the RNA too sticky?

Krishnamurthy and others have partially doubted the RNA World hypothesis; because RNA molecules could be too “sticky” to serve as the first self-replicators.

An RNA chain can pull other independent RNA building blocks attached to it to biçim some kind of mirror image sequence. Each building block in the new strand is attached to the complementary building block on the original “template” strand.

If the new thread can separate from the template thread and begin to template other new threads with the same process, then she özgü attained life’s underlying self-replicating skill.

But while RNA strands may be good at template complementary strands, they are not so good at detaching from these strands.

Çağdaş organisms make enzymes that can force twin strands of RNA, or DNA, to go their separate ways, thus making it possible to coagulate; however, it is not clear how this could be done in a world where enzymes do not yet exist.

A chimeric solution

Krishnamurthy and colleagues have argued in recent studies that “chimeric” molecular strands, part DNA and part RNA, may have overcome this sorun; because they showed that the complementary strands mold less adhesively, allowing them to separate relatively easily.

Chemists have also shown in widely cited articles over the past few years that the simple ribonucleoside and deoxynucleoside building blocks of RNA and DNA, respectively, may have emerged in the early Earth under very similar chemical conditions.

What’s more, they reported in 2017 that the organic compound DAP could play a pivotal role in modifying ribonucleosides and sequencing them into the first strands of RNA.

The new study shows that under similar conditions, DAP can do the same for DNA.

“We’ve found that using DAP to react with deoxynucleosides works better when deoxynucleosides are not all the same, but rather mixtures of different DNA“ letters ”like real DNA such as A and T or G and C,” says researcher Eddy Jiménez.

Krishnamurthy: “Now that we understand better how primitive chemistry made the first RNAs and DNAs, we can begin to use it on ribonucleoside and deoxynucleoside building blocks to see which chimeric molecules were formed and whether they could replicate and evolve and develop on their own.” says.

He also notes that the study can have wide practical applications. For example, artificial synthesis of DNA and RNA in the “PCR” technique underlying COVID-19 tests means a huge global business; however, it depends on enzymes that are relatively fragile and therefore have many limitations.

Compiled by: Feyza ÇETİNKOL

Kaynak: sciencedaily

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