Global alignment: Difference between revisions

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In the process of global-global alignment, a DNA or a query sequence dictates the length of putative [[homologs]]. Based on sequence similarity to query, the top matches are generated by a given algorithm. The entire length of a given match must bear similarity to the entire length of query sequence. Any sequence having partial similarity to query is excluded from the matches.
Global alignment allows sequences to be aligned from start to end. A scoring matrix is build with ''n'' sequences aligned on''n''axes. Each entry in a given cell is matched with corresponding entries in''n'' dimensions. Consequently, each cell has a score depending upon the threshold values selected for registering a match or a mismatch. A pointer is drawn in a cell that indicates the direction from which the highest score was obtained. In the end, starting from bottom right of matrix the arrows are back tracked to the origin. This gives the best order in which ''n'' sequences should be globally aligned.
In case of global-local alignment, the word "global" applies to the query and "local" applies to the hit. A given match has only partial similarity to the query such that the entire length of a match aligns partially with query.

Revision as of 22:11, 25 September 2009

Global alignment allows sequences to be aligned from start to end. A scoring matrix is build with n sequences aligned onnaxes. Each entry in a given cell is matched with corresponding entries inn dimensions. Consequently, each cell has a score depending upon the threshold values selected for registering a match or a mismatch. A pointer is drawn in a cell that indicates the direction from which the highest score was obtained. In the end, starting from bottom right of matrix the arrows are back tracked to the origin. This gives the best order in which n sequences should be globally aligned.