First universal common ancestor
First universal common ancestor
Main page

First universal common ancestor

logo
Community Hub0 subscribers
What are your thoughts?
Be the first to start a discussion here.
Be the first to start a discussion here.
First universal common ancestor

The first universal common ancestor is thought to be a non-cellular entity that was the earliest organism with a genetic code capable of biological translation of RNA molecules into peptides to produce proteins. Its descendants would include the last universal common ancestor (LUCA) and every modern cell. FUCA would also be the ancestor of ancient sister lineages of LUCA, none of which have modern descendants, but which are thought to have horizontally transferred some of their genes into the genome of early descendants of LUCA.

FUCA is thought to have been composed of progenotes, proposed ancient biological systems that would have used RNA for their genome and self-replication. By comparison, LUCA would have had a complex metabolism and a DNA genome with hundreds of genes and gene families.

Long before the appearance of compartmentalized biological entities like FUCA, life had already begun to organize itself and emerge in a hypothesized pre-cellular era known as the RNA world. The universal presence of both biological translation mechanism and genetic code in every biological systems indicates monophyly, a unique origin for all biological systems including viruses and cells.

FUCA is thought to have been the first organism capable of biological translation, using RNA molecules to convert information into peptides and produce proteins. This first translation system would have been assembled together with primeval, possibly error-prone genetic code. That is, FUCA would be the first biological system to have genetic code for proteins.

The development of FUCA likely took a long time. FUCA was generated without genetic code, from the ribosome, itself a system evolved from the maturation of a ribonucleoprotein machinery. FUCA appeared when a proto-peptidyl transferase center started to first emerge, when RNA world replicators started to be capable to catalyze the bonding of amino acids into oligopeptides.

The first genes of FUCA were most likely encoding ribosomal, primitive tRNA-aminoacyl transferases and other proteins that helped to stabilize and maintain biological translation. These random peptides produced possibly bound back to the single strand nucleic acid polymers and allowed a higher stabilization of the system that got more robust and was further bound to other stabilizing molecules. When FUCA had matured, its genetic code was completely established.

It has been said FUCA was composed by a population of open-systems and a population of self-replicating ribonucleoproteins. With the arrival of these systems, began the progenote era. These systems evolved into maturity when self-organization processes resulted in the creation of a genetic code. This genetic code was for the first time capable to organize an ordered interaction between nucleic acids and proteins through the formation of a biological language. This caused pre-cellular open systems to then start to accumulate information and self-organize, producing the first genomes by the assembly of biochemical pathways, which probably appeared in different progenote populations evolving independently.

In the reduction hypothesis, where giant viruses evolved from primordial cells that became parasitic, viruses might have evolved after FUCA and before LUCA.

See all
User Avatar
No comments yet.