130 ORIGIN OF LIFE Miller–Urey experiment (or Miller experiment) An experiment carried out by Stanley Miller and Harold Urey in 1952, which demonstrated the synthesis of amino acids in conditions simulating a thunderstorm on the early Earth The experiment can be seen as marking the beginning of the experimental study of the chemistry of life’s origins Nucleic acid The molecules that carry genetic information – DNA and RNA Phylogeny The evolutionary relationships between different species of organism, represented in the form of a phylogenetic tree In molecular phylogeny these relationships are determined by analysing the differences in the sequences of genes common to the various species Pre-RNA world A hypothetical early stage in the development of life, which preceded the RNA world and used some other genetic material in place of RNA or DNA Ribosomal RNA The RNA components of a ribosome One of these components, the small subunit ribosomal RNA (also known as 16S ribosomal RNA in prokaryotes or 18S ribosomal RNA in eukaryotes), has been widely used to determine the tree of life Ribosome A structure composed of protein and RNA molecules that reads genetic information from messenger RNA and synthesizes the corresponding protein Ribozyme An RNA molecule that acts as a catalyst The discovery of RNA catalysis led to a Nobel prize for Sidney Altman and Thomas Cech, and to the concept of the RNA world RNA Ribonucleic acid; a molecule that can carry genetic information in a similar way to DNA In modern cells, RNA molecules are important in the process of protein synthesis, in the form of messenger RNA, ribosomal RNA, and transfer RNA RNA world A hypothetical early stage in the development of life, in which RNA molecules provided both the genome and the catalysts, roles that were subsequently taken over by DNA and proteins Stromatolites Layered structures built by colonies of micro-organisms that are commonly found in the Archaean and Proterozoic fossil records Modern examples can be found in sites such as Shark Bay in Western Australia Tree of life A phylogenetic tree covering all groups of life on Earth The term is commonly used for the tree derived by molecular phylogeny using small subunit ribosomal RNA, as pioneered by Carl Woese in the 1970s See Also Atmosphere Evolution Biosediments and Biofilms Earth Structure and Origins Evolution Famous Geologists: Cuvier; Darwin Precambrian: Eukaryote Fossils; Prokaryote Fossils Tectonics: Hydrothermal Vents At Mid-Ocean Ridges Further Reading Bailey J (2001) Astronomical sources of circularly polarized light and the origin of homochirality Origins of Life and Evolution of the Biosphere 31: 167 183 Davies P (1998) The Fifth Miracle London: Penguin Books De Duve C (1995) Vital Dust New York: Basic Books Ferris JP (1998) Catalyzed RNA synthesis for the RNA world In: Brack A (ed.) The Molecular Origins of Life, pp 255 268 Cambridge: Cambridge University Press Kasting JF and Brown LL (1998) The early atmosphere as a source of biogenic compounds In: Brack A (ed.) The Molecular Origins of Life, pp 35 56 Cambridge: Cambridge University Press Miller S (1953) A production of amino acids under possible primitive Earth conditions Science 117: 528 529 Miller SL and Lazcano A (2002) Formation of the building blocks of life In: Schopf JW (ed.) Life’s Origin, pp 78 112 Berkeley: University of California Press Orgel LE (2002) The origin of biological information In: Schopf JW (ed.) Life’s Origin, pp 140 157 Berkeley: University of California Press Stetter K (1998) Hyperthermophiles and their possible role as ancestors of modern life In: Brack A (ed.) The Molecular Origins of Life, pp 315 335 Cambridge: Cambridge University Press Wills C and Bada J (2000) The Spark of Life New York: Perseus Publishing Woese CR, Kandler O, and Wheelis ML (1990) Towards a natural system of organisms: proposal for the domains Archaea, Bacteria and Eucarya Proceedings of the National Academy of Sciences USA 87:4576 4579 Yusupov MM, Yusupova GZ, and Baucom A (2001) Crys tal structure of the ribosome at 5.5A˚ resolution Science 292: 883 896