Diversity and Phylogenetic Implications of Cscl Profiles From
Molecular Phylogenetics and Evolution Vol. 17, No. 2, November, pp. 219–230, 2000 doi:10.1006/mpev.2000.0838, available online at http://www.idealibrary.com on Diversity and Phylogenetic Implications of CsCl Profiles from Rodent DNAs Christophe Douady,*,†,1 Nicolas Carels,*,‡ Oliver Clay,*,‡ Franc¸ois Catzeflis,† and Giorgio Bernardi*,‡,2 *Laboratoire de Ge´ne´ tique Mole´ culaire, Institut Jacques Monod, Tour 43, 2 Place Jussieu, F-75005 Paris, France; †E´ quipe Phyloge´ nie Mole´ culaire, Laboratoire de Pale´ ontologie, Institut des Sciences de l’E´ volution, UMR 5554/UA 327, CNRS, Universite´ de Montpellier II, Case 064, Place Euge` ne Bataillon, F-34095 Montpellier cedex, France; and ‡Stazione Zoologica Anton Dohrn, Villa Comunale, I-80121 Naples, Italy Received December 13, 1999; revised July 17, 2000 INTRODUCTION Buoyant density profiles of high-molecular-weight DNAs sedimented in CsCl gradients, i.e., composi- The long, compositionally homogeneous regions of tional distributions of 50- to 100-kb genomic frag- which mammalian genomes consist, the isochores ments, have revealed a clear difference between the (ӷ300 kb on average), belong to a small number of 3 murids so far studied and most other mammals, in- families. Within any isochore family, GC levels of 50- cluding other rodents. Sequence analyses have re- to 100-kb regions, or fragments, vary little (2–3% GC); vealed other, related, compositional differences be- yet, together these isochore families span a wide GC tween murids and nonmurids. In the present study, we range, from 30 to 60% (Macaya et al., 1976; Thiery et obtained CsCl profiles of 17 rodent species represent- al., 1976; Cuny et al., 1981; Bernardi et al., 1985; ing 13 families.
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