e-value in BLASTn search - (Sep/30/2005 )
hi
i know that the e-value in BLASTn gives the probability a query beeing similer to a NCBI seq by chance and 0 e-value means good match. I have a sequence that has 4e-45. can someone help me to understand this?
thanks
cheer
chnadima
-chandima-
QUOTE (chandima @ Sep 30 2005, 11:02 AM)
hi
i know that the e-value in BLASTn gives the probability a query beeing similer to a NCBI seq by chance and 0 e-value means good match. I have a sequence that has 4e-45. can someone help me to understand this?
thanks
cheer
chnadima
i know that the e-value in BLASTn gives the probability a query beeing similer to a NCBI seq by chance and 0 e-value means good match. I have a sequence that has 4e-45. can someone help me to understand this?
thanks
cheer
chnadima
Could be the right gene of a different organism. Or a perfect match, but only for a limited length (short query?).
-Theo22-
4e-45 is Fortran shorthand for 4 x 10^(-45), a very small number. For relatively short sequences, this might be the result of a perfect match. Even if it is not a perfect match, it is a very good match, and indicates either an extremely similar sequence, or possibly a single sequencing error or point mutation in a perfect match.
-phage434-