Last Universal Common Ancestor (LUCA)

LUCA - Important Facts:
  • Also known as the 'Last Universal Ancestor' (LUA); and also cenancestor (from the Greek root cen. together) proposed by Fitch in 1987.
  • The most recent organism from which all living organisms on Earth descend.
  • It is also the 'Most Recent Common Ancestor' (MRCA) of all life on Earth.
  • Estimated to have lived around 3.5 billion - 3.8 billion years ago (Paleoarchean era).
  • New evidence suggests that LUCA may have had a primitive RNA genetic code which would have been more sensitive to increased environmental temperatures compared with DNA. [1]
  • It was only later that DNA was incorporated into the ancestors, perhaps via viruses, allowing cells to survive in more extreme environments.
Was there a LUCA?
  • We do not know.
  • We may never know, because there may not have been a single ancestor.
  • Some experts believe that LUCA may actually be a mess ('cellular mist') of different gene-swapping early cells.
Common Features Found in Living Organisms:
  • Genetic code is based on DNA.
  • Genetic code is expressed via RNA intermediates.
  • Proteins are expressed from the genetic code.
  • The proteins are made from amino acids by translation of an mRNA by ribosomes, tRNA and a group of related proteins.
  • There are only 20 amino acids that are used.
  • ATP is used as an energy intermediate.
  • A lipid bilayer (cell membrane) surrounds the cell.
  • There is a ionic gradient inside the cell for sodium and potassium.
  • The cell can multiply by initially duplicating its contents, followed by cellular division.
  1. Bastien Boussau, Samuel Blanquart, Anamaria Necsulea, Nicolas Lartillot, Manolo Gouy. Parallel adaptations to high temperatures in the Archaean eon. Nature, 2008; 456 (7224): 942 DOI: 10.1038/nature07393

Posted by ALCHEssMIST.
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