What is the last universal common predecessor (Luca)?
The latest universal common predecessor (Luca) is a hypothetical ancient microbe from which it descends the whole contemporary life. About 60,000 years ago, a man lived in Africa, from which all living people descend. Luca is a thought based on a similar principle, but it is more of an ordinary predecessor of all life than just people. It is assumed that Luca lived between 3.6 and 4.1 billion years. Life may have existed for 100-500 million years before Luca appeared. Luca is not the first living thing ever, or the most primitive living organism, only the universal common predecessor of all existing organisms.
Although fossils from the period are modest and highly degraded, we can extrapolate the characteristics of Luca by seeing what features have in common today. This includes a genetic code based on two-string DNA, including four nucleotides, which consists of 64 possible three-nucleotide codons. This selection of nucleotides is arbitrary, but but universal to the whole earthly life.
Another shared feature is the way DNA instructions are expressed through single -thread intermediates of RNA. These intermediates RNA lead to the construction of ribosomes, thorn and a group of proteins related. These proteins are built of 20 amino acids and the synthesis pathways are arbitrary but universal. All life forms use glucose (simple sugar) as a source of energy and carbon. ATP is always used as an energy currency of cells. Luca would have a simple locomotive system based on microtubules.
It is uncertain whether Luca is more similar to bacteria of domain or archaea. Both have extremely primitive variants. Until 2002, it was assumed that bacteria, mycoplasma genitalium had the shortest genome of all living things, consisting of 582,970 pairs of bases. Then the title stole Nanoar Archaea Chaeum Equitans , with 490 885 pairs of basic pairs. In 2006, Candidatus bacteriaRuddii again took the title with a genome only 159,662 couples. Luca probably had genomic complexity in this general extent.