[Rb(2.6)4IEM: a new Robertsonian marker translocation in Mus musculus laboratory mice].

A detailed cytogenetic analysis of mice, both heterozygous and homozygous, for a new translocation of a spontaneous origin has been performed. The differential staining of mitotic and meiotic chromosomes, and the analysis of F1-hybrides proved that this translocation of Robertsonian type resulted from the centromeric fusion between chromosomes 2 and 6 of the normal karyotype. According to the standards for genetic nomenclature of laboratory mouse, the translocation is called Rb(2.6)4IEM (Institute for Experimental Medicine). A stock of laboratory mice homozygous for two different Robertsonian translocation - Rb(2.6)4IEM and Rb(8.17)1IEM has been obtained (2n = 36, NF = 40). Feasible mechanisms of chromosomal rearrangements leading to new translocations of the Robertsonian type in laboratory mice are discussed.