The Major Compositional Transitions
in the Vertebrate Genome
G. Bernardi, S. Hughes, D. Mouchiroud
Journal of Molecular Evolution,
44, S44-S51 (1997)
Abstract
The vertebrate genome underwent two major
compositional transitions, between therapsids and
mammals and between dinosaurs and birds. These
transitions concerned a sizable part (roughly
one-third) of the genome, the gene-richest part of
it, and consisted in an increase in GC levels (GC is
the molar fraction of guanine + cytosine in DNA)
which affected both coding sequences (especially
third codon positions) and noncoding sequences. These
major transitions were studied here by comparing GC3
levels (GC3 is the GC of third codon positions) of
orthologous genes from Xenopus, chicken, calf, and man.
