Relationship between GC content and the relative amino acid usage in chicken.

For each gene, the relative amino acid usage (RAAU), the GC content of the CDS (GCcds), the GC content at the first, second and third position (GC1, GC2 and GC3), were calculated by codonW 1.4.2. We also retrieved all intronic sequences for each gene and provided the combined length of all introns for a gene exceeding 200 bp and calculated the GC content of the intronic sequences (GC introns). The linear regression analyses were made between RAAU and GCcds, GC1, GC2, GC3 and GC introns for each amino acid. The regression coefficients were presented on the table. In order to determine this 5 variables contributing to the amino acid usage and how they may interact, we performed multiple linear regressions with these variables, excluding those not contributing significantly through the use of the t-statistical logarithm with backward stepwise regression. The adjusted R-square for each amino acid was given in the last column. * represents P>0.05.Relationship between GC content and the relative amino acid usage in chicken.