Question

Which of the given statements is incorrect about Cluster analysis?

(a) Clustering organizes the proteins into groups by some objective criterion

(b) One criterion for a matching protein pair is the statistical significance of their alignment score

(c) The P or E value from BLAST searches cannot be the criterion for a matching protein pair

(d) A criterion for clustering proteins is the distance between each pair of sequences in a multiple sequence alignment

The question was posed to me in semester exam.

The query is from Comparative Genomics in section Collecting & Storing Sequences in Laboratory of Bioinformatics

Answer 1

Correct choice is (c) The P or E value from BLAST searches cannot be the criterion for a matching protein pair

The explanation is: Option c and b mean the same yet are different by the negation in option c.The lower this value, the better the alignment. There will be a cutoff P or E value at which the matches in the BLAST search are no longer considered significant. A value of P or E = 0.01–0.05 is usually the point at which the alignment score is no longer considered to be significant in  order to focus on a more closely related group of proteins.