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In molecular biology and bioinformatics, the consensus sequence is the calculated order of most frequent residues, either nucleotide or amino acid, found at each position in a sequence alignment. It represents the results of a multiple sequence alignments in which related sequences are compared to each other and similar sequence motifs are calculated. Such information is important when considering sequence-dependent enzymes such as RNA polymerase.[1]

Biological significance[edit]

A protein binding site, represented by a consensus sequence, may be a short sequence of nucleotides which is found several times in the genome and is thought to play the same role in its different locations. For example, many transcription factors recognize particular patterns in the promoters of the genes they regulate. In the same way restriction enzymes usually have palindromic consensus sequences, usually corresponding to the site where they cut the DNA. Transposons act in much the same manner in their identification of target sequences for transposition. Finally splice sites (sequences immediately surrounding the exon-intron boundaries) can also be considered as consensus sequences.

Thus a consensus sequence is a model for a putative DNA binding site: it is obtained by aligning all known examples of a certain recognition site and defined as the idealized sequence that represents the predominant base at each position. All the actual examples shouldn't differ from the consensus by more than a few substitutions, but counting mismatches in this way can lead to inconsistencies.[2]

Any mutation allowing a mutated nucleotide in the core promoter sequence to look more like the consensus sequence is known as an up mutation. This kind of mutation will generally make the promoter stronger, and thus the RNA polymerase forms a tighter bind to the DNA it wishes to transcribe and transcription is up-regulated. On the contrary, mutations that destroy conserved nucleotides in the consensus sequence are known as down mutations. These types of mutations down-regulate transcription since RNA polymerase can no longer bind as tightly to the core promoter sequence.

Sequence analysis[edit]

Developing software for pattern recognition is a major topic in genetics, molecular biology, and bioinformatics. Specific sequence motifs can function as regulatory sequences controlling 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.

Notation[edit]

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}YR

In this notation, A means that an A is always found in that position; [CT] stands for either C or T; N stands for any base; and {A} means any base except A. Y represents any pyrimidine, and R indicates any purine.

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 logos the more conserved the residue, the larger the symbol for that residue is drawn; the less frequent, the smaller the symbol. Sequence logos can be generated using WebLogo, or using the Gestalt Workbench, a publicly available visualization tool written by Gustavo Glusman at the Institute for Systems Biology.[2]

Software[edit]

Bioinformatics tools are able to calculate and visualize consensus sequences. Examples of the tools are JalView and UGENE.

See also[edit]

References[edit]

  1. ^ Pierce, Benjamin A. 2002. Genetics : A Conceptual Approach. 1st ed. New York: W.H. Freeman and Co.
  2. ^ a b Schneider TD (2002). "Consensus Sequence Zen". Appl Bioinformatics 1 (3): 111–119. PMC 1852464. PMID 15130839. 

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Consensus_sequence — Please support Wikipedia.
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77 news items

 
Nature.com
Mon, 02 Mar 2015 07:46:12 -0800

For each library for which we had average coverage of the mitochondrial genome of at least tenfold after removal of duplicated molecules, we built a mitochondrial consensus sequence, assigning haplogroups for each library as described in Supplementary ...
 
GenomeWeb
Mon, 23 Feb 2015 12:37:30 -0800

Then they error-correct these reads using the partial order aligner or POA software, which applies a directed acyclic graph to compute a multiple alignment to determine a consensus sequence. The corrected reads are then fed into the Celera assembler.
 
GenomeWeb
Thu, 22 Jan 2015 11:30:00 -0800

For the second, they allowed multiple alignments to the reference for each read, enabling them to "gather all reads for a single gene in a single pileup to any of the eight HLA-A/B loci to generate a consensus sequence." Several variant and haplotype ...
 
Science Careers Blog (subscription)
Thu, 11 Sep 2014 11:07:04 -0700

Stephen K. Gire, Augustine Goba, Kristian G. Andersen, Rachel S. G. Sealfon, Daniel J. Park, Lansana Kanneh, Simbirie Jalloh, Mambu Momoh, Mohamed Fullah, Gytis Dudas, Shirlee Wohl, Lina M. Moses, Nathan L. Yozwiak, Sarah Winnicki, Christian B.

Phys.Org

The Daily Galaxy (blog)
Mon, 29 Sep 2014 09:07:30 -0700

One method is called consensus-sequence engineering, and is the more simplistic of the two. Scientists just plug the sequence of a protein of interest into a protein database. The query returns a large number of “hits,” or analogous sequences.
 
HealthCanal.com
Sun, 13 Jul 2014 15:07:30 -0700

Researchers have found that viral protein sequences matching a consensus sequence, which is hypothesized to be most fit, are more likely to be transmitted than those that deviate from the consensus. The results were published Thursday in Science.

Healthline

Healthline
Thu, 10 Jul 2014 15:30:00 -0700

... to establish an infection. The bottleneck means that when a person becomes infected, he or she is exposed to many strains of HIV, but they are quickly whittled down to only the strongest — the one that most closely resembles the "consensus ...
 
GenomeWeb
Sun, 16 Nov 2014 18:11:44 -0800

In a paper published in PLoS One last month, the researchers described the method, which involves iteratively weaving PacBio long reads into a consensus sequence to fill in missing bits of sequence between contigs in a scaffold in a reference-guided ...
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