Inferring BLAST Tutorial
After clicking on RUN BLAST, formatting BLAST page appears.It tells you about the
conserved domain (if any) present in protein sequence. If you scroll down more you can change the settings for the results page.I guess
default settings are OK.
Click on the FORMAT button for the results page.
New window appears and according to your sequence length, computer and
Internet speed this page might take time.
Now finally how to infer your blast results?
“Results of BLAST”
There is a graphical representation which shows many colorful lines,these lines
are nothing but the hits with the query sequence.
The score of each alignment is indicated by one of five different colors,
which divides the range of scores into five groups
Put your mouse on individual lines without clicking it and you will find definition of
the protein. On clicking on it you will see the complete description of the alignment.
Scroll below the graphical representation and you’ll find matches which have significant
similarity with the query sequence. The first match is the query protein sequence itself which is quite obvious.
Each line has the name of the protein, score in bits and E value (i.e., Expect value).
The sequence should be selected for
lower e-value and higher score.
Let’s study one example-
So when you click here you will find that this is a protein sequence of Dihydrofolate
reductase of Rat, which shares 89% identity.
Now you can see identity and other features by clicking on the respective score bit number.
In this case click on 348.
There is difference between identity and positives as Identity refers to the exact
number of matches with the query sequence and the database sequence and Positives refer to the amino acids
which are similar according to their physiochemical property.
Doing BLAST searches one can infer about the function of the unknown protein
which provides more insight to a particular protein. Certainly experimental validation is a must.
If you want to study more about BLAST parameters or any other features
in BLAST .GO to NCBI BLAST tutorial.