Question

If all the nucleotides are present with equal frequencies and at random, what are the chances of having a particular four nucleotide long motif?

(a) 1/256

(b) 1/64

(c) 1/16

(d) 1/8

I have been asked this question in an interview.

My question is from Restriction Endonuclease & Phosphatases topic in section Basics of Genetic Engineering of Genetic Engineering

Answer 1

The correct option is (a) 1/256

The explanation is: There are four nucleotide bases present in a DNA sequence A, T, C and G. If the bases are present with equal frequency and at random the chances of having a particular 4 nucleotide long motif is 1/ (4*4)= 1/256.