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Robertsonian fusion and X chromosome polymorphism in Zygodontomys (= Bolomys) lasiurus (Cricetidae, Rodentia) from central Brazil

Marta Svartman; Eunice Judith Cardoso de Almeida

Departamento de Biologia, Instituto de Biocências, Universidade de São Paulo, Caixa Postal 11461, 05422-970 São Paulo, Brasil. Send correspondence to E.J.C.A.

ABSTRACT

Nineteen specimens of Zygodontomys (- Bolomys) lasiurus were analyzed cytogenetically and two karyotypes were identified (2n-34, FN-34; 2n-33, FN-34). An heterozygous fusion/fission involving pairs 6 and 7, responsible for the variation in the diploid number, was detected. X chromosome polymorphism was also present and three kinds of X, one acrocentric (Xa) and two subtelocentrics (Xb and Xc), were identified. C-banding patterns and chromosomal measurements led to the conclusion that gradual mechanisms of constitutive heterochromatin additions/deletions are responsible for this polymorphism.

Keywords: Robertsonian fusion; X chromosome polymorphism; Zygodontomys lasiurus; Rodentia.

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