Question

Which of the following is untrue about Expectation Maximization (EM) method?

(a) It is used to find hidden motifs

(b) The method works by first making a random or guessed alignment of the sequences to generate a trial PSSM

(c) The trial PSSM is used to compare with each sequence individually

(d) The log odds scores of the PSSM are modified at the end of the process

I had been asked this question in unit test.

My doubt stems from Motif Discovery in Unaligned Sequences in section Sequence Alignment of Bioinformatics

Answer 1

Correct option is (d) The log odds scores of the PSSM are modified at the end of the process

The explanation is: The log odds scores of the PSSM are modified in each iteration to maximize the alignment of the matrix to each sequence. During the iterations, the sequence pattern for the conserved motifs is gradually “recruited” to the PSSM.