Consensus sequence Guide, Meaning , Facts, Information and Description
In molecular biology and bioinformatics, a consensus sequence is a way of representing the results of a multiple sequence alignment, where related seqeunces are compared to each other, and similar functional sequence motifs are found. The concensus sequence shows which residues are conserved (are always the same), and which residues are variable.
Developing software for pattern recognition is a major topic in genetics, molecular biology, and bioinformatics. Specific sequence motifs can function as regulatory sequences controling biosynthesis, or as signal sequences that direct a molecule to a specific site within the cell or regulate its maturation. Since the regulatory function of these sequences is important, they are thought to be conserved across long periods of evolution. In some cases, evolutionary relatedness can be estimated by the amount of conservation of these sites.
The conserved sequence motifs are called consensus sequences and they show which residues are conserved and which residues are variable. Consider the following example DNA sequence:
A[CT]N{A}
In this notation, A means that always an A is found in that position. [CT] stands for either C or T, N stands for any base, and {A} means any base except A.
In this example, the notation [CT] does not give any indication of the relative frequency of C or T occurring at that position. An alternative method of representing a consensus sequence uses a sequence logo. This is a graphical representation of the consensus sequence, in which the size of a symbol is related to the frequency that a given nucleotide (or amino acid) occurs at a certain position. In sequence logo's the more conserved the residue, the larger the symbol for that residue is drawn, the less frequent, the smaller the symbol. Sequence logo's can be generated using the Gestalt Workbench, a publically available visualization tool written by Gustavo Glusman at the Institute for Systems Biology.