Exploring Genomics Data > Aiptasia > Tools and Resources > Bioinformatic Resources > Performing a BLAST search

Performing a BLAST Search

Basic Local Alignment Search Tool, or BLAST, is a tool that enables a researcher to search through large databases of sequences to find all sequences that are similar to a sequence-of-interest. Blast works by taking the researcher's sequence of interest (called the query sequence), and comparing it to every sequence in a large database of sequences. Blast evaluates the degree of similarity and then pulls out all sequences that share at least a small region of similarity to the query. The researcher must evaluate the list of sequences to make a determination as to whether blast hits really represent true homologs. The BLAST algorithm was developed and implemented by Stephen Altschul at the U.S. National Center for Biotechnology Information.

Questions I must be able to answer in order to perform a blast search:

  1. What sequence(s) are the subject of my research? These are called query sequences. Example: I am examining the potential roles of the 10 most abundant sequences in the Aiptasia transcriptome sequence dataset. I will use these as the query sequences in a blast search.
  2. What subject database is the most appropriate to search, given my research question?
blast algorithms

How to perform a blast search:

Step 1: Retrieve a query sequence you want to use and make sure it is in fasta format
Step 2: Navigate to the database you want to search against
Step 3: Select the BLAST programthat will use the query sequence to search the database that you selected.
Step 4: Adjust any parameters, as appropriate

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