Indeed, for some categories, the correlation coefficients of the ω-degree correlation attain values that are comparable with (or even surpass) those for the ω-expression level and/or the ω-expression breadth correlations (table 2).
In fact, some categories exhibit strong negative ω-degree correlations that are comparable in strength to (or even stronger than) the ω-expression level and the ω-expression breadth correlations (tables 1 and 2).
Here, we investigate the rate-breadth correlation using the data on orthologous proteins from Drosophila and Mammalia.
Such sites evolve at above-average rates, due to lack of selective constraint, and all amino acids are acceptable at them, leading to a positive rate-breadth correlation.
Therefore, at expression breadth ≤10, correlation became maximum and most reliable.
Characterizing promoter architecture through the presence of CpG-islands and TATA-boxes, we confirmed that CpG+/TATA- promoter presence is positively correlated with expression breadth (Pearson's correlation coefficient = 0.394, P < 10-15), while CpG-/TATA+ and CpG-/TATA- promoters show a corresponding negative correlation (Additional file 1, Figure S1a).
Interestingly, many properties that correlate with expression breadth also correlate with phyletic age and vice versa; indeed, some studies have reported correlations between phyletic age and expression breadth [ 2, 4].
The authors state in the Background that "A priori, it is not obvious how the rate and the breadth are correlated across sites and proteins", but in the rest of the study seem to express mild surprise that the correlation between rate and breadth is so weak.
Second, we assessed the influence of gene expression breadths on the correlation between CpG O/E and gene lengths, using partial correlation (Kim and Yi 2006, 2007).
The RSCU' of one translationally weak codon correlates negatively with maximum expression, but has no significant positive or negative correlation with breadth of expression, and there is only one exception (GTA coding for Valine).
Åstebro and Thompson (2011) and Oberschachtsiek (2009) examined whether the correlation between breadth of human capital investments and entrepreneurship was due instead to a taste for variety.
