Tag: DNA

New Findings Suggest the Building Blocks For Life’s Genetic Structure May Well Have Arrived From Above

Conceptual image of meteoroids delivering nucleobases to ancient Earth. The nucleobases are represented by structural diagrams with hydrogen atoms as white spheres, carbon as black, nitrogen as blue and oxygen as red. (NASA Goddard/CI Lab/Dan Gallagher)

All of life, from simplest to most complex, contains five information-passing compounds that allow the genetic code to work.  These nitrogen-based compounds, called nucleobases, are found in all the the DNA and RNA that  provide the instructions to build and operate every living thing on Earth.

How these compounds are formed, or where they come from, has long been a key question in astrobiology and the search for the origin of life.

Numerous theories have been advanced to explain their presence, including that they arrived on Earth via meteorites and the infall of dust.  But until recently, only three of these nucleobases have been found embedded in meteorites but, puzzlingly, the two others have not been found.

Now an international team centered in Japan has completed the search for nucleobases in meteorites by finding the remaining two, and so it appears possible that all these building blocks of the genetic code could have arrived on very early Earth from afar.

Yasuhiro Oba of the University of Hokkaido, and lead author of the new study in Nature Communications, said that  extraterrestrial material arrived in much greater quantities on the early Earth — during what is called the period of “late heavy bombardment” — and so the discovery “of all five primary nucleobases in DNA/RNA indicates that these components should have been provided to the early Earth with such extraterrestrial materials.”

This certainly does not mean that fully formed DNA or RNA was delivered to Earth.  Oba said the process of making those nucleic acids from components parts, including nucleobases, is under active study but is not particularly well understood.  But it does mean that essential building blocks for the genetic backbone of life clearly did arrive from space for possible use in the life-forming process.

“We don’t know how life first started on the Earth, but the discovery of extraterrestrial nucleobases in meteorites provides additional support for the theory that meteorite delivery could have seeded the early Earth with the fundamental units of the genetic code found in DNA and RNA in all life today,” said co-author Daniel Glavin of NASA’s Goddard Spaceflight Center.

“These nucleobases are highly soluble in liquid water, so over time, any meteorite fragments exposed to water on the early Earth would be extracted from the meteorites into the water and could therefore contribute to the chemical inventory of the prebiotic soup from which life emerged.”… Read more

In Search of Panspermia (and Life on Icy Moons)

 

Sometimes personal affairs intervene for all of us, and they have now for your Many Worlds writer and his elderly father.  But rather than remain off the radar screen, I wanted to repost this column which has a new import. 

It turns out that versions of the instrument described below — a miniature gene sequencing device produced by Oxford Nanopore — have been put forward as the kind of technology that could detect life in the plume of Enceladus, or perhaps on Europa or Titan. 

Major figures in the astrobiology field, including Steve Benner of the Foundation for Applied Molecular Evolution (FfAME) and Chris McKay of NASA Ames Research Center see this kind of detection of the basic polymer backbone of RNA or DNA life as a potentially significant way forward.  Three different “Icy Moon” teams are vying for a NASA New Frontiers mission to Enceladus and Titan, and this kind of technology plays a role in at least one of the proposed missions.

 

Early Earth, like early Mars and no doubt many other planets, was bombarded by meteorites and comets. Could they have arrived "living" microbes inside them?

Early Earth, like early Mars and no doubt many other planets, was bombarded by meteorites and comets. Could they have arrived “living” microbes inside them?

When scientists approach the question of how life began on Earth, or elsewhere, their efforts generally involve attempts to understand how non-biological molecules bonded, became increasingly complex, and eventually reached the point where they could replicate or could use sources of energy to make things happen.  Ultimately, of course, life needed both.

Researchers have been working for some time to understand this very long and winding process, and some have sought to make synthetic life out of selected components and energy.  Some startling progress has been made in both of these endeavors, but many unexplained mysteries remain at the heart of the processes.  And nobody is expecting the origin of life on Earth (or elsewhere) to be fully understood anytime soon.

To further complicate the picture, the history of early Earth is one of extreme heat caused by meteorite bombardment and, most important, the enormous impact some 4.5 billion years of the Mars-sized planet that became our moon.  As a result, many early Earth researchers think the planet was uninhabitable until about 4 billion years ago.

Yet some argue that signs of Earth life 3.8 billion years ago have been detected in the rock record, and lifeforms were certainly present 3.5 billion years ago.  Considering the painfully slow pace of early evolution — the planet, after all, supported only single-cell life for several billion years before multicellular life emerged — some

dna animation. the big 300

A DNA helix animation.

Read more

© 2022 Many Worlds

Theme by Anders NorenUp ↑