DNA may have had humble beginnings as nutrient carrier

5 hours ago by Adam Hadhazy An artists impression of a DNA molecule. Credit: FBI

New research intriguingly suggests that DNA, the genetic information carrier for humans and other complex life, might have had a rather humbler origin. In some microbes, a study shows, DNA pulls double duty as a storage site for phosphate. This all-important biomolecule contains phosphorus, a sometimes hard-to-get nutrient.

Maintaining an in-house source of phosphate is a newfound tactic for enabling microorganisms to eke out a living in harsh environments, according to a new study published in the open-access, peer reviewed scientific journal PLOS ONE. The finding bodes well for life finding a way, as it were, in extreme conditions on worlds less hospitable than Earth.

The results also support a second insight: DNA might have come onto the biological scene merely as a means of keeping phosphate handy. Only later on in evolutionary history did the mighty molecule perhaps take on the more advanced role of genetic carrier.

"DNA might have initially evolved for the purpose of storing phosphate, and the various genetic benefits evolved later," said Joerg Soppa, senior author of the paper and a molecular biologist at Goethe University in Frankfurt, Germany.

Unraveling life's origins

Scientists continue to investigate the development of self-replicating, intricate sets of chemistryin other words, lifefrom the chemical compounds thought available on early Earth. Out of this mixture of prebiotic chemicals, two nucleic acidsRNA and DNAemerged as champions.

Today, these two types of biomolecules serve as the genetic information carriers for all Earthly biota. RNA on its own suffices for the business of life for simpler creatures, such as some viruses. Complex life, like humans, however, relies on DNA as its genetic carrier.

Astrobiologists want to understand the origin of DNA and its genetic cousin, RNA, because figuring out how life got started here on Earth is key for gauging if it might ever develop on alien planets.

Many researchers think RNA must have preceded DNA as the genetic molecule of choice. RNA is more versatile, acting as both genetic code and a catalyst for chemical reactions. Explicating the rise of DNA as a genetic material directly from RNA, however, is tricky. Compared to RNA, DNA needs significantly more supporting players for it to work well in a biological setting.

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DNA may have had humble beginnings as nutrient carrier