Answer:
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. There are 20 amino acids used in making proteins, but only four different bases to be used to code for them.
Obviously one base can't code for one amino acid. That would leave 16 amino acids with no codes.
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.
However, if you took three bases per amino acid, that gives you 64 codes (TTT, TTC, TTA, TTG, TCT, TCC and so on). That's enough to code for everything with lots to spare. You will find a full table of these below.
A three base sequence in DNA or RNA is known as a codon.
The code in DNA
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).
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.
Explanation:
