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Computational approaches to sequence alignment generally fall into two categories: global alignments and local alignments. Calculating a global alignment is a form of global optimization that "forces" the alignment to span the entire length of all query sequences. By contrast, local alignments identify regions of similarity within long ...
Multi-alignment; Full automatic sequence alignment; Automatic ambiguity correction; Internal base caller; Command line seq alignment: Nucleotides: Local or global: Heracle BioSoft SRL: 2006 (latest version 2018) Commercial (some modules are freeware) DNADynamo: linked DNA to Protein multiple alignment with MUSCLE, Clustal and Smith-Waterman ...
The Needleman–Wunsch algorithm is still widely used for optimal global alignment, particularly when the quality of the global alignment is of the utmost importance. However, the algorithm is expensive with respect to time and space, proportional to the product of the length of two sequences and hence is not suitable for long sequences.
Multiple sequence alignment (MSA) is the process or the result of sequence alignment of three or more biological sequences, generally protein, DNA, or RNA. These alignments are used to infer evolutionary relationships via phylogenetic analysis and can highlight homologous features between sequences.
The rest of this article is focused on only multiple global alignments of homologous proteins. The first two are a natural consequence of most representations of alignments and their annotation being human-unreadable and best portrayed in the familiar sequence row and alignment column format, of which examples are widespread in the literature.
Sequence alignment can also reveal conserved domains and motifs. One motivation for local alignment is the difficulty of obtaining correct alignments in regions of low similarity between distantly related biological sequences, because mutations have added too much 'noise' over evolutionary time to allow for a meaningful comparison of those regions.
A global alignment performs an end-to-end alignment of the query sequence with the reference sequence. Ideally, this alignment technique is most suitable for closely related sequences of similar lengths. The Needleman-Wunsch algorithm is a dynamic programming technique used to conduct global alignment. Essentially, the algorithm divides the ...
Global alignments are constructed using ClustalW on the sequences, two at a time, and sed to give one full-length alignment between each pair of sequences. The local alignments are the ten top-scoring non-intersecting local alignments gathered using the Lalign program of the FASTA package.