## BLAST

**Moderators:** Leonid, amiradm, BioTeam

### BLAST

Hi everyone!

I'm a little confused about some categories in NCBI's Blast. I did a nucleotide Blast. In the "Description" section it gives me a Max score and a Total score. I know how the BLAST score is calculated, but I don't understand how these two values are derived.

I've been doing some googling and I find definitions like this:

But it still doesn't make sense to me. Can anyone offer a better definition or explain these definitions?

Thanks for your help

I'm a little confused about some categories in NCBI's Blast. I did a nucleotide Blast. In the "Description" section it gives me a Max score and a Total score. I know how the BLAST score is calculated, but I don't understand how these two values are derived.

I've been doing some googling and I find definitions like this:

1.) "Max score". The score of the highest scoring HSP from that

database sequence.

2.) "Tot score". The total score of all HSP's from that database

sequence.

But it still doesn't make sense to me. Can anyone offer a better definition or explain these definitions?

Thanks for your help

### Re: BLAST

I found this page that gives the definitions of total score and max score: http://www.digitalworldbiology.com/BLAST/slide7.html

I just wish I had some one explain to me how the total score can be bigger than the max score. I need an example you know?

I just wish I had some one explain to me how the total score can be bigger than the max score. I need an example you know?

Whew. Success.

I have a subject sequence containing two HSPs with the following statistics

Score = 276 bits (149), Expect = 4e-70

Identities = 149/149 (100%), Gaps = 0/149 (0%)

Strand=Plus/Plus

and...

Score = 156 bits (84), Expect = 6e-34

Identities = 84/84 (100%), Gaps = 0/84 (0%)

Strand=Plus/Plus

The Max score is 276 bits and the Total score is 276 + 156 = 432 bits

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