Question

For the 10-residue DNA sequence example, there are _______ possible starting sites for a 20-residue-long site.

(a) 30

(b) 21

(c) 81

(d) 60

This question was addressed to me by my college director while I was bunking the class.

Origin of the question is Statistical Methods for Aiding Alignment topic in section Multiple Sequence Alignment of Bioinformatics

Answer 1

Correct option is (c) 81

Explanation: For the 10-residue DNA sequence example, there are 100 – 20 +1 possible starting sites for a 20-residue-long site. Where the first one is at position 1 in the sequence ending one at 20 and the last beginning at position 81 and ending at 100 (there is not enough sequence for a 20-residue-long site beyond position 81).