A sequence logo is a graphical representation of a set of nucleotide sequences that are binding sites for proteins or other macromolecules. The logo uses letters of differing size to display the relative frequencies of alternative bases at each position in the sequence, so that information about variation in the sequence motif is not lost as it is in a conventional consensus sequence. This keyword site contains logos for many sequence motifs that are important in gene expression. Check out the logos for yeast TATA boxes as well as the splice donor and splice acceptor sites in human RNA processing to judge how strongly the "consensus sequences" are conserved.

Cystic fibrosis is among the most common serious inherited human disorders. It results from any of a number of mutations resulting in a defect in the cystic fibrosis transmembrane conductance regulator (CFTR), one of a family of membrane chloride channels. The gene is designated CFTR. The mutant allele of CFTR most frequently encountered in patients is DF508, a deletion of three nucleotides that deletes a phenylalanine at position 508 in the CFTR polypeptide chain. Although the DF508 deletion accounts for about two-thirds of the mutant CFTR alleles in the human population, more than 700 mutant alleles have been described. Most of these are listed at this keyword site. Note the great variety of different types of mutations that have been described: promoter mutation, amino acid replacement, frameshift mutation, splicing defect, deletion, and so forth.

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