Introduction: BLAST1 of 2
NCBI BLAST allows you to input a sequence from DNA, RNA or protein residues (amino acids) and find sequences that are identical or similar.
To get to BLAST from the NCBI home page, click BLAST from the Popular Resources menu bar on the right of the page.
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You can also get to BLAST directly by going to http://blast.ncbi.nlm.nih.gov/
Identifying Sequences with BLAST1 of 3
There are many options on the Standard Nucleotide BLAST page. For example, you can select different databases to search; you can exclude certain data sources; and you can select a specific algorithm by which to search.
For your first BLAST, we will keep this very basic. We will mostly use the default options to enter a sequence string, and we'll use BLAST to identify the organism it came from, and see what else we can learn about it.
Identifying Sequences with BLAST2 of 3
Copy and paste the entire string of nucleotide symbols, below, into the box under Enter Query Sequence.
Uncheck this box labeled "Align two more sequences" if it is checked:
then scroll down and click the BLAST button:
Identifying Sequences with BLAST3 of 3
You may need to be patient.
BLAST is crunching a huge amount of data.
You will see a screen like this for a while during processing:
Reading your BLAST Results1 of 2
Once your results are displayed, you will see a header followed by the results of your search. The results can be displayed in several different views, including a list of sequence "Descriptions," via a "Graphic Summary," and via a more detailed "Alignments" view.
Select the Graphic Summary by clicking on this tab:
to see a graphic summary of the top 100 results.
Reading your BLAST Results2 of 2