center Genotype and Phenotype

Genetic Code

Flow of Information
The Genetic Code is ...
... stored on one of the two strands of a DNA molecules as a linear, non-overlapping sequence of the nitrogenous bases Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). These are the "alphabet" of letters that are used to write the "code words".

The genetic code consists of a sequence of three letter "words" (sometimes called 'triplets', sometimes called 'codons'), written one after another along the length of the DNA strand.

Each code word is a unique combination of three letters (like the ones shown above) that will eventually be interpreted as a single amino acid in a polypeptide chain. There are 64 code words possible from an 'alphabet' of four letters.

One of these code words, the 'start signal' begins all the sequences that code for amino acid chains. Three of these code words act as 'stop signals' that indicate that the message is over. All the other sequences code for specific amino acids.

Some amino acids are only coded for by a single 'word', while some others are coded for by up to four 'words'. The genetic code is redundant.

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Science at a Distance
© 1997, 1998, 1999, 2000 Professor John Blamire