Calculate the JukesCantor Corrected dNdS for the following a

Calculate the Jukes-Cantor Corrected dN/dS for the following alignment between two species of a small protein-coding gene (the reading frame starts at the first position)

Species 1: TTTACCGATCAAGTT

Species 2: CTTACGGAACAAATT

What type of selection, if any, do you observe? Explain your answer with one sentence.

Solution

The Jukes-Cantor formula gives the dS/dN ratio, which is the ratio of the number of synonymous (dS) and non-synonymous (dN) substitution per site. Here 2 nonsynonymous and 3 synonymous substitutions are there. The dN/ dS ratio is =2/3, i. e. less than 1, which indicates negative selection.