File:Effect of genome streamlining on the ratio of nonsynonymous to synonymous substitutions.webp

English: "In populations of Mycoplasma mycoides after 2000 generations of evolution, we used the normalized ratio of nonsynonymous to synonymous mutations (dN/dS) as an indicator of natural selection. Values of dN/dS > 1 are associated with positive selection, while values of dN/dS < 1 are associated with the dominance of negative selection and constraint on adaptation. The minimal and non-minimal cell exhibited comparable values of dN/dS (t6 = 0.81, P = 0.488). One of the replicate populations belonging to the non-minimal treatment had an elevated dN/dS (2.06) compared to other replicate populations (mean dN/dS = 0.45). When we removed this potential outlier, there was still no difference in dN/dS between the minimal and non-minimal cell (t5 = −0.25, P = 0.811). Dark-coloured symbols represent the mean ± SEM (n = 4). Light-coloured symbols represent individual values for each replicate population (n = 4). Hypotheses were evaluated with two-sided t-tests. Source Data"