Part IV: using BLAST

Instructions:

1. Go to http://blast.ncbi.nlm.nih.gov/Blast.cgi

2. Click on nucleotide BLAST.

3. Copy STS mRNA query sequence from the week 3 links page then paste it into the

Query sequence window (note that this is a nucleotide sequence).

4. Under Database, choose Standard databases

5. Choose optimize for somewhat similar sequences (blastn) under Program selection,

(note this is not the default) then click BLAST.

6. Now, run the same query against the expressed sequence tags database (est).

(Database "Others", then scroll to "expressed sequence tags")

Questions:

1. What are the names, scores, and e-values of your best hits for the two different

searches you just performed?

2. Why are these results so different?