title: A relationship between GC content and coding-sequence length.
abstract: Since base composition of translational stop codons (TAG, TAA, and TGA) is biased toward a low G+C content, a differential density for these termination signals is expected in random DNA sequences of different base compositions. The expected length of reading frames (DNA segments of sense codons flanked by in-phase stop codons) in random sequences is thus a function of GC content. The analysis of DNA sequences from several genome databases stratified according to GC content reveals that the longest coding sequences-exons in vertebrates and genes in prokaryotes-are GC-rich, while the shortest ones are GC-poor. Exon lengthening in GC-rich vertebrate regions does not result, however, in longer vertebrate proteins, perhaps because of the lower number of exons in the genes located in these regions. The effects on coding-sequence lengths constitute a new evolutionary meaning for compositional variations in DNA GC content.
authors.affiliation: Departamento de Genética, Instituto de Biotecnología, Facultad de Ciencias, Universidad de Granada, E-18071-Granada, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Oliver
authors.forename: A
authors.initials: A
authors.lastname: Marín
mesh_terms: D000818:Animals; D001419:Bacteria / Q000235:genetics; D001482:Base Composition; D001483:Base Sequence; D002417:Cattle; D002645:Chickens; D003062:Codon; D003596:Cytosine; D004247:DNA / Q000737:chemistry* / Q000235:genetics; D004926:Escherichia coli; D005091:Exons; D006147:Guanine; D006801:Humans; D007438:Introns; D051379:Mice; D008957:Models, Genetic; D014176:Protein Biosynthesis; D051381:Rats; D016364:Reading Frames; D012984:Software
chemical_list: D003062:Codon; D006147:Guanine; D003596:Cytosine; D004247:DNA