Evolutionary genomics of vertebrates and its implications.
The discovery that the vertebrate genomes of warm-blooded vertebrates are mosaics of isochores, long DNA segments homogeneous in base composition, yet belonging to families covering a broad spectrum of GC levels, has led to two major observations. The first is that gene density is strikingly non-uniform in the genome of all vertebrates, gene concentration increasing with increasing GC levels. (Although the genomes of cold-blooded vertebrates are characterized by smaller compositional heterogeneities than those of warm-blooded vertebrates and high GC levels are not attained, their gene distribution is basically similar to that of warm-blooded vertebrates.) The second observation is that the GC-richest and gene-richest isochores underwent a compositional transition (characterized by a strong increase in GC level) between cold- and warm-blooded vertebrates. Evidence to be discussed favors the idea that this compositional transition and the ensuing highly heterogeneous compositional pattern was due to, and was maintained by, natural selection.
D'Onofrio
G
G
Laboratoire de Génétique Moléculaire, Institut Jacques Monod 2, Paris, France. donofrio@alpha.szn.it
Jabbari
K
K
Musto
H
H
Alvarez-Valin
F
F
Cruveiller
S
S
Bernardi
G
G
D000818:Animals; D019143:Evolution, Molecular; D006801:Humans; D014714:Vertebrates / Q000235:genetics*