BLAST Search Instructions
In the middle of the page under the Basic BLAST heading, click protein blast. A new page will appear.
Copy the amino acid sequence from above (BLAST ignores numbers and spaces) and paste it in the Enter Query Sequence box at the top of the new page.
In the Choose Search Set box, in the pull-down menu to the right of Database, choose the database Non-redundant protein sequence (nr).
In the text box to the right of Organism, type "Homo sapiens," and then click on Homo sapiens (taxid: 9606).
In the Program Selection box, choose blastp (protein-protein BLAST).
In the lower left of the screen (you may need to scroll down), click the BLAST button. Wait for BLAST to complete the search. Initial information (Conserved Domains) may appear quickly, but display of the full results may take 30 seconds. (If your search returns a screen that displays “No significant similarity found,” open Hint 1 to see what might have gone wrong.)
A new screen displays your search results. Briefly scroll down to look at the three main sections, and notice the type of information that is provided in each section. Note that in each of the three sections, similar sequences, or hits, are listed beginning with the best statistical match to your query sequence.
The Graphic Summary gives a color-based summary of the sequence alignment between your query sequence and the most similar sequences (hits). (For this exercise, you can ignore the conserved domains information at the top.)
The Descriptions section provides the unique accession number of each hit, a brief description of the sequence, and several “scores” that quantify the similarity between each hit and your query sequence.
The Alignments section shows the alignment between each hit and your query sequence, amino acid by amino acid.
Scroll to the top of the Graphic Summary section, but ignore the conserved domains information. Place your cursor over the top red bar that represents the first hit. Look at the information in the small text box immediately above the Graphic Summary figure. For an explanation of what appears in the text box, see Hint 2.
[Screenshot from BLAST]
Scroll down to the first entry in the Descriptions section. Notice that the information from the text box above the Graphic Summary matches the information in the Accession, Description, Max score (the same as the S value in the text box), and E value columns.
Scroll back up to the Graphic Summary. Again, place your cursor over the top red bar and click on it. This links you to the information in the Alignments section for this hit. Your hit will appear at the top of the screen beginning with its accession number and description.
Based on the information given in the three different sections, which of the following statement(s) correctly describe(s) the hit that is most similar to the query sequence? Select all that apply.
Based on the information given in the three different sections, which of the following statement(s) correctly describe(s) the hit that is most similar to the query sequence? Select all that apply.
a) It contains a total of 491 amino acids.
b) It is identical to the query sequence in length and amino acid sequence.
c) It is a chimeric protein.
d) Its accession number is CAM33009.1.
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