Universal code

Human mitochondrial DNA (mtDNA), a circular supercoiled DNA of about 16,469 base pairs, codes for 13 proteins, 22 tRNAs, and 2 ribosomal RNAs (rRNAs) using a code slightly different from the virtually universal code (page... 

The universal code is very useful in the biotech industry- we can make human proteins in other animals and plants. 

Some minor exceptions to the universal code are found in mitochondrial chloroplast DNA and in a few protozoa. 

The LOINC system is a universal coding system for reporting laboratory and other clinical observations to fachitate... 

The genetic code of mitochondria is not the same as the universal code, which has implications for the evolution of mitochondria. Human mitochondria contain a set of tRNA molecules that are not found elsewhere in the... 

AUA and AUU are initiation codons, as is AUG. Both AUA and AUG also code for methionine. AUU also codes for isoleucine, as in the universal code. 

Maize mitochondria use CGG for tryptophan rather than for arginine, and CGU, CGC, and CGA for arginine. Yeast mitochondria use CUX, where X is any base, for threonine rather than for leucine. Both maize and yeast use AGA and AGG for arginine. Evidently, various mitochondrial codes can differ from each other as well as from the universal code. 

The number of mammalian mitochondrial tRNA molecules is 22, which is less than the minimum number (32) needed to translate the universal code. This is possible because in each of the fourfold redundant sets—e.g., the four alanine codons GCU, GCC, GCA, and GCG—only one tRNA molecule (rather than two, as explained above) is used. In each set of four tRNA molecules, the base in the wobble position of the anticodon is U or a modified U (not I). It is not yet known whether this U is base-paired in the codon-anticodon interaction or manages to pair weakly with each of the four possible bases. For those codon sets that are doubly redundant—e.g., the two histidine codons CAU and CAC—the wobble base always forms, a G-U pair, as in the universal code. The structure of the human mitrochondrial tRNA molecule is also different from that of the standard tRNA molecule (except for mitochondrial tRNA UUX). (X = any nucleotide.) The most notable differences are the following ... 

It became apparent during the 1960s that this recognition mechanism was not confined to viruses or bacteria but was the universal code for the synthesis of proteins throughout the living world. 

To avoid implying something that is not in fact true, I repeat a point made briefly in Chapter 2, that mitochondria get many of their proteins from the host cell, and these proteins are coded in the nucleus with the usual universal code. The proteins that are coded by the mitochondrial DNA constitute a small fraction of the proteins that work in the mitochondria.) Second, the small nnmber of mitochondrial genes makes it mnch more likely than it would be for the nuclear DNA that certain codons shonld fall into disuse as a simple statistical fluctuation, thereby facilitating the sort of mechanism I have just discussed. These sorts of considerations suggest that it is quite possible that the mitochondrial variations arose after the universal code became established, thongh they do not, of course, exclude the alternative supposition that they are survivals of extremely ancient versions of the code. 

M. Gordon, C.E. Kendall, W.H.T. Davison, Chemical Ciphering A Universal Code as an Aid to Chemical Systematics, Royal Institute of Chemistry of Great Britain and Ireland, London, 1948. 

J. Rissanen, Universal Coding. Information. Prediction, and Estimation. IEEE Transformation on Information Theory 30 (1984). 629-636. 

Some of the most important features of the code can be specified by saying that the genetic message is contained in a triplet, nonoverlapping, commaless, degenerate, universal code. Each of these terms has a definite meaning that describes the way in which the code is translated. 

A universal code is one that is the same in all organisms. The universality of the code has been observed in viruses, prokaryotes, and eukaryotes. However, there are some exceptions. Some codons seen in mitochondria are different... 

The universal genetic code has been viewed from the time of its discovery 50 years ago as a frozen accident. Some organelle genomes show a deviation from this universal code. Do these genomes provide evidence for this view of the code ... 

Brown, W.F., et. al.. Aerospace Structural Metals Handbook, CINDAS/Purdue University, code 4112, 1992 ed. 

A further interesting feature of mitochondria is that their protein-translating system shows certain fundamental differences from those of bacteria and eukaryotes. Thus it operates with only 22 types of transfer RNA instead of 31 or more and four of the 64 codons have different meanings from those of the Universal code (page 301). 

University codes may be very succinct. For example, the U.S. Military Academy s Cadet Honor Code is simply stated as A cadet will not lie, cheat, steal, or tolerate those who do. According to the USM A, On a behavioral level, the Code represents a simple standard for all cadets. On a developmental plane. West Point expects that all cadets will strive to live far above the minimum standard of behavior and develop a commitment to ethical principles guiding moral actions. Besides it succinctness, the USMA s honor code is closely linked to the academy s core mission which is to develop leaders of character for our Army... A leader of character will apply the Spirit of the Code when making decisions involving ethical dilemmas. ... 

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