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.
Laboratoire de Génétique Moléculaire, Institut Jacques Monod 2, Paris, France. donofrio@alpha.szn.it
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G
D'Onofrio
K
K
Jabbari
H
H
Musto
F
F
Alvarez-Valin
S
S
Cruveiller
G
G
Bernardi
D000818:Animals; D019143:Evolution, Molecular; D006801:Humans; D014714:Vertebrates / Q000235:genetics*