The dS has been used to approximate the nucleotide substitution rate under neutral evolution (e.g., Lynch and Conery 2000) because synonymous substitutions by definition do not change amino acids and therefore are under weak, if any, selective pressure.
Whilst synonymous mutations by definition do not alter the primary amino acid sequence of a gene product, some perform regulatory roles including transcription enhancement, microRNA targeting and alternative splicing (Goode et al. 2010; Lin et al. 2011).
Dispelling entrenched views that feminism "is synonymous with man-hating," Emma Watson proclaimed that "feminism by definition is the belief that men and women should have equal rights and opportunities".
For many people it's synonymous with confrontation or that one-dimensional, zero-sum game where by definition if one person wins, the other person loses.
In fact when we excluded heterozygous sites, which by definition are polymorphic, we found a significant elevation in the proportion of non-synonymous to synonymous polymorphisms in both selfing genotypes (the P N / P S ratio rises from 0.41 in the outcrosser to 0.43 in the Jamaican selfer and 0.47 in the Nicaraguan selfer, χ = 18.3, 2 DF, P <0.001).
To confirm our finding of positive selection, we evaluated the robustness of our results to several tree topologies (including the phylogeny reconstructed with amino acid sequences, which by definition tends to minimize the number of non-synonymous changes).
A pseudogene – which by definition can hardly ever be under purifying selection – would not show a bias to synonymous over non-synonymous mutations, and its sequence would most likely show nucleotide insertion or deletion.
Caddies, by definition, are contractors.
A celebrity by definition.
They are, by definition, short.
