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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.
References:
  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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