In fact there are only two amino acids which have only one sequence of bases to code for them - methionine (Met) and tryptophan (Trp). There are six different codons all of which will eventually produce a leucine (Leu) in the protein chain. Look, for example, at leucine in the first column. The colours are to stress the fact that most of the amino acids have more than one code. It is fairly obvious how it works and, in any case, it doesn't take very long just to scan through the table to find what you want. The table is arranged in such a way that it is easy to find any particular combination you want. The table shows how the various combinations of three bases in the coding strand of DNA are used to code for individual amino acids - shown by their three letter abbreviation. The codes in the coding strand of DNA and in messenger RNA aren't, of course, identical, because in RNA the base uracil (U) is used instead of thymine (T). You will find a full table of these below.Ī three base sequence in DNA or RNA is known as a codon. That's enough to code for everything with lots to spare. However, if you took three bases per amino acid, that gives you 64 codes (TTT, TTC, TTA, TTG, TCT, TCC and so on). If you took two bases to code for each amino acid, that would still only give you 16 possible codes (TT, TC, TA, TG, CT, CC, CA and so on) - still not enough. That would leave 16 amino acids with no codes. Obviously one base can't code for one amino acid. There are 20 amino acids used in making proteins, but only four different bases to be used to code for them. You can think of the sequences of bases in the coding strand of DNA or in messenger RNA as coded instructions for building protein chains out of amino acids. Unless you just want a quick reference to get the coding for a particular amino acid, it would pay you to start from the beginning with the structure of DNA. Note: If you have come straight to this page from a search engine, you should be aware that this is the fourth page in a sequence of pages about DNA and RNA. It is designed for 16 - 18 year old chemistry students. This page looks at how the base sequences in DNA and RNA are used to code for particular amino acids when it comes to building protein chains.
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