E-value in Blast

[pavan]

Hello everybody!!

How blast results very with change in e-value.
If i change e-value from 10 to directly to some value like e10-6(0.000001)


Thanks
Pa1

[GenoMax]

I am not sure if there is a question in your post or a statement but if that was a question then refer following:

http://blast.ncbi.nlm.nih.gov/Blast.cgi?CMD=Web&PAGE_TYPE=BlastDocs&DOC_TYPE=FAQ#expect

http://www.ncbi.nlm.nih.gov/BLAST/tutorial/Altschul-1.html

[Melissa]

You are asking how does reducing the E-value change your blast results if I understand correctly. When you change the E-value from 10 to 1E-6, you will remove results which are less significant and thus, you get lower number of results. The smaller the E-value, the more significant is the result. The smallest E-value you can get is 0.0. If two results contain E-value 0.0, I would look at the scores to find the most significant results.

[A_Morozov]

Yeah, one more thing to keep in mind. E-value setting does not affect parameters of the alignment, it just makes BLAST display more or less hits.