Karyotype analysis of male rat (Rattus rattus ) fromAmalner, Maharashtra

Asurvey of literature on karyotype analysis of male black rat (Rattus rattus) indicates that there is no unique consensus on number and morphology of chromosomes. Several workers have reported the diploid chromosome number (2N) in black rat as 38, 40 and 42. It was found that different strains of laboratory rats showed differences in the morphology of chromosomes. Because of the fragment demonstration of chromosomes polymorphism and the geographic variations at its karyotype, the black rat (Common house rat) has proved to be an interesting animal for chromosomal studies. The present investigation was undertaken with an objective of determining its diploid chromosome number and describing the nature of its chromosomes. The Rattus rattus was administered with 0.02% of colchicine for inducing mitosis. After 2 hours of colchicine treatment, the rat was sacrificed by using anesthetic ether and dissected out the femurs. The present experimental results indicated that the diploid chromosome number of Rattus rattus is 2n=38 and the karyotype formula is16m+ 4sm+ 16a +1X+1Y.