DNA sequencing. Computer print-out of the sequence of bases in a sample of DNA (deoxyribonucleic acid). The sequence, which makes up the genetic code, is shown graphically and as a code of letters; each code of letters refers to the graph beneath it. The four bases which make up the cross-linking strands in DNA are: guanine (G), cytosine (C), thymine (T) and adenine (A). The information contained within a genome, the full set of genes (specific segments of DNA), determines every physical characteristic of an organism. Mutations in the genome can be the cause of inherited diseases such as cystic fibrosis.