Your friend runs a BLASTp on his unknown sequence and finds a match with E-value of 3 with a target. What does this mean?
Your friend runs a BLASTp on his unknown sequence and finds a match with E-value of 3 with a target. What does this mean?
Select an option to attempt
Correct Answer: Option D
Explanation
BLASTp E-value of 3 — interpretation:The E-value (Expect value) represents the number of alignments of equal or better score expected by CHANCE alone in a database of that size:• E-value = 3 means: You would expect to find 3 hits of this score or better just by random chance.• This is a HIGH E-value → the match is NOT statistically significant → likely a coincidental match.Common misconceptions:• E-value ≠ number of mismatches: mismatches affect the alignment SCORE (not directly the E-value).• E-value is NOT a probability in the 0–1 range (it CAN be >1).• E-value ≠ '1 in 3 chance': the probability interpretation would be; for small E,, but for E=3,.Conclusion: E-value = 3 means 3 random hits expected by chance alone → this match is NOT biologically meaningful.Answer: E-value of 3 means 3 similar hits are expected by random chance; the match is NOT significant.