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The RNA world hypothesis places RNA at center-stage when life originated. The RNA world hypothesis is supported by the observations that ribosomes are ribozymes: [120] [121] the catalytic site is composed of RNA, and proteins hold no major structural role and are of peripheral functional importance. This was confirmed with the deciphering of ...
In the late 1960s, Orgel proposed that life was based on RNA before it was based on DNA or proteins. His theory included genes based on RNA and RNA enzymes. [17] This view would be developed and shaped into the now widely accepted RNA world hypothesis. Almost thirty years later, Orgel wrote a lengthy review of the RNA World hypothesis. [18]
The period followed the hypothesized RNA world and ended with the formation of DNA and contemporary proteins. [2] In the RNP world, RNA molecules began to synthesize peptides. These would eventually become proteins which have since assumed most of the diverse functions RNA performed previously. This transition paved the way for DNA to replace ...
In the eocyte hypothesis, the organism at the root of all eocytes may have been a ribocyte of the RNA-world. For cellular DNA and DNA handling, an "out of virus" scenario has been proposed: storing genetic information in DNA may have been an innovation performed by viruses and later handed over to ribocytes twice, once transforming them into bacteria and once transforming them into archaea.
Transitions described in the book Transition from: Transition to: Notes Replicating molecules "Populations" of molecules in compartments Can't observe [clarification needed] Independent replicators (probably RNA) Chromosomes: RNA world hypothesis: RNA as both genes and enzymes: DNA as genes; proteins as enzymes Prokaryotes: Eukaryotes
The genetic code may have evolved during the transition from the RNA world to a protein world. [86] The Alanine World Hypothesis postulates that the evolution of the genetic code (the so-called GC phase [87]) started with only four basic amino acids: alanine, glycine, proline and ornithine (now arginine). [88]
RNA-based evolution is a theory that posits that RNA is not merely an intermediate between Watson and Crick model of the DNA molecule and proteins, but rather a far more dynamic and independent role-player in determining phenotype.
Metabolism here means a cycle of chemical reactions that produce energy in a form that can be harnessed by other processes. The idea is that once a primitive metabolic cycle was established, it began to produce ever more complex compounds. His model is known as the iron-sulfur world theory by analogy with the RNA world hypothesis.