Genetical Research



The non-random occurrence of Robertsonian fusion in the house mouse


ELODIE GAZAVE a1c1, JOSETTE CATALAN a1, MARIA DA GRAÇA RAMALHINHO a2, MARIA DA LUZ MATHIAS a3, ANA CLAUDIA NUNES a3, DAVID DUMAS a1, JANICE BRITTON-DAVIDIAN a1 and JEAN-CHRISTOPHE AUFFRAY a1
a1 Institut des Sciences de l'Evolution, UMR CNRS, CC 064, Université de Montpellier II, 34095 Montpellier cedex 5, France
a2 Centro de Biologia Ambiental, Museu Nacional de Historia Natural, Rua de Escola Politecnica, 1200 Lisbon, Portugal
a3 Centro de Biologia Ambiental, Departamento de Zoologia e Antropologia da Faculdade de Ciências da Universidade de Lisboa, Edificio C2, 3° piso, Campo Grande, 1749-016, Lisbon, Portugal

Abstract

Chromosomal rearrangements such as Robertsonian (Rb) fusions constitute a major phenomenon in the evolution of genome organization in a wide range of organisms. Although proximate mechanisms for the formation of Rb fusion are now well identified, the evolutionary forces that drive chromosomal evolution remain poorly understood. In the house mouse, numerous chromosomal races occur in nature, each defined by a unique combination of Rb fusions. Among the 106 different Rb fusions that were reported from natural populations, the low involvement of chromosome 19 in Rb fusions is striking, prompting the question of the randomness of chromosomal involvement in Rb fusions. We uncover a significant quadratic relationship between chromosome size and probability of fusing, which has never previously been in this species. It appears that fusions involving chromosome 19 are not particularly infrequent, given the expected low fusion probability associated with the chromosome's size. The results are discussed, assessing selective processes or constraints that may operate on chromosome size.

(Received July 17 2002)
(Revised October 23 2002)


Correspondence:
c1 Tel: +33 4 67 14 47 82. Fax: +33 4 67 14 36 10. e-mail: gazave@isem.univ-montp2.fr


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