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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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114 news items

 
Nature.com
Wed, 29 Jul 2015 03:21:31 -0700

454C>T). Bioinformatics and functional analyses provided novel information on three of these variants. c.-429C>G potentially disrupts a consensus sequence for a terminal oligopyrimidine tract, whereas c.-244C>T may alter the RNA secondary structure in ...
 
GenomeWeb
Tue, 14 Jul 2015 11:54:25 -0700

To date, most genomic studies of papillomaviruses have used Sanger sequencing to look at the "most prevalent, consensus sequence" during chronic infection, but Sanger sequencing may "not be appropriate to capture the dynamics of slowly evolving ...
 
Nature.com
Fri, 24 Jul 2015 05:04:26 -0700

The identified Ser20 site on CHIP resides in (S/T)PX(K/R), the highly conserved consensus sequence for the phosphorylation across species (Supplementary Figure 2). To further confirm whether Cdk5 phosphorylates CHIP at Ser20 in vivo, we raised a rabbit ...

Nature.com

Nature.com
Wed, 08 Jul 2015 08:00:03 -0700

The human RLBP1 transgene sequence used in the vectors was based on the coding portion of the human RLBP1 gene mRNA sequence (NCBI Reference Sequence: NM_000326). In all vectors with a transgene, the Kozak consensus sequence, GCCACC, ...
 
Journal of Virology
Wed, 08 Jul 2015 07:48:45 -0700

To determine the genetic differences responsible, the consensus sequence of L10 was determined and compared to that of SFV4. Of the 12 nucleotide differences, six were nonsynonymous; these were engineered into a new molecular clone, termed SFV6.

Fred Hutch News Service

Fred Hutch News Service
Mon, 18 May 2015 11:00:00 -0700

The authors then generated a consensus sequence for each group: Cen1-like and Cen13-like. Several sequences also matched unplaced clones from the human genome assembly. These abundant sequences were composed of two a-satellite repeats ...
 
Nature.com
Fri, 29 May 2015 06:02:10 -0700

Here we present evidence that both GLI1 and GLI2, the final effectors of HH signaling, regulate the transcription factor E2F1 in melanoma cells, by binding to a functional non-canonical GLI consensus sequence. Consistently, we find a significant ...

BMC Blogs Network (blog)

BMC Blogs Network (blog)
Fri, 17 Apr 2015 03:16:37 -0700

“At the time, I was fortunate that Alan Scott was developing a consensus sequence of human L1 elements just two floors above my lab. What's more, Jef Boeke in Molecular Biology at Hopkins, was an expert who coined the term retrotransposition during ...
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