To better characterise and understand the evolution of GC content patterns in vertebrate coding sequences under the influence of GC-biased gene conversion (a meiotic repair bias that favours G and C over A and T alleles in high-recombining genomic regions), transcriptome analysis of five reptilian species (the golden tegu Tupinambis teguixin, the green iguana Iguana iguana, the Boa constrictor, the Jesus Christ lizard Basiliscus plumifrons and the Nile crocodile Crocodylus niloticus), two birds (the great tit Parus major and the emperor penguin Aptenodytes forsteri) and one amphibian (the fire salamander Salamandra salamandra) was carried out by RNA-Seq.