Computation of the information loss score for variations in the protein-coding DNA. (a) Deletion of DNA base "A" at site 143 of the human protein PTEN causes a reading frame-shift (depicted by an arrow to the left on DNA sequence) that results in the mistranslation of all residues after the mutation. An alignment of homologous proteins is used to measure the biological information content of the reference sequence (PTEN in the figure) and to measure the loss of information due to this mistranslation. (b) A NM at the DNA site 910 on the human protein NF1 causes a premature stop codon at the residue 304 (denoted by *). The mutant protein is missing residues after the premature stop codon.