Resumen de G-banding of the genus Rattus (rodent, Muridae) in Tunisia, occurrence of different banding of the sexual chromosome Y in the norvegicus species

Aymen Ben Ibrahim, Imed Ben Salem, M'barek Chetoui, Saïd Nouira

• The two species of rats Rattus rattus and Rattus norvegicus are the only representatives of the genus Rattus in Tunisia. R. rattus is represented by a karyotye 2n = 38 to 39 chromosomes, it belongs to the oceanic type, whereas R. norvegicus has a karyotype of 2n = 42 chromosomes.

  The G-bands produced by these two species are specific; the ideogram representation of the chromosomes shows 136 bands for R. rattus and 189 bands for R. norvegicus, the number of the bands for each species is lower than those identified in Europe. Based on the comparison of the various G-banding profiles, we can confirm that for R. rattus, the integration of the acrocentrics pairs 4/7 and 11/12 by two robertsonian fusions and the two pericentric inversions of acrocentric pairs 1 and 9, who have infected the asian type, give respectively the two large metacentric pairs and the two subtelocentric pairs (1 and 9) characteristic of the oceanic type and the B chromosome is completely heterochromatic. For R.

  norvegicus, the change of the position between the dark and clear bands of the sexual chromosome Y is the remarkable opposite of the one identified in Europe.