Codon usage patterns in chromosomal and retrotransposon genes of the mosquito Anopheles gambiae

Codon usage was compiled for fourteen chromosomal genes and four retrotransposons from the mosquito Anopheles gambiae. Variation exists among chromosomal genes in the degree of bias. The genes showing the highest bias are probably most highly expressed. In these genes, the base composition at the third codon position is much richer in G + C than is the overall coding sequence. Thus, codon usage is biased toward G- or C-ending codons. Codon usage in each retrotransposon is quite different, not only from chromosomal genes but also from the other retrotransposons. Codon usage comparisons among homologous genes from An. gambiae and two other Dipterans, the yellow fever mosquito Aedes aegypti and the fruitfly Drosophila melanogaster, show that while there are similarities, particularly between An. gambiae and D. melanogaster in the preference for G-and C-ending codons, each species has evolved a distinct pattern of codon usage.