BLAST searches

The Basic Local Alignment Tool (BLAST) is an efficient computer program for comparing DNA and protein sequences. There are several flavors of BLAST available:
  1. blastp compares an amino acid query sequence against a protein sequence database
  2. blastn compares a nucleotide query sequence against a nucleotide sequence database
  3. blastx compares a nucleotide query sequence translated in all reading frames against a protein sequence database
  4. tblastn compares a protein query sequence against a nucleotide sequence database dynamically translated in all reading frames
  5. tblastx compares the six-frame translations of a nucleotide query sequence against the six-frame translations of a nucleotide sequence database.
Not all flavors are available at all times. The six-frame translations require a lot of processor time and are often limited in usage.

In the following pages we will discover the power of BLAST searches for comparing DNA sequences, protein sequences, and DNA seqeunces against protein sequences.

Please check these pages out:

  1. Basic information about the BLAST search, how it is done (briefly), what the scores mean, what the databases are, and what the input sequences are.
  2. How to do a BLAST search with a description of the basic BLAST search.
  3. Understanding BLASTN results
  4. Understanding BLASTP results
  5. Understanding BLASTX results
  6. simple BLAST with ESTs
  7. more powerful BLAST with ESTs
  8. Minimum percent identities with different BLAST DNA scoring matrices

As always, comments and suggestions to Rob Edwards

Created 3/11/01 by Rob Edwards