抄録
Karyotype of Rattus norvegicus, Berkenhout from Indian environs is reported for the first time. The diploid number is found to be 42 with XX/XY sex determining mechanism X is a medium telocentric chromosome ranking 6th or 7th in order of size and constitutes 5.45% of the total haploid set. The size of the Y is found to be variable. It is either the smallest telocentric or equal to the medium size telocentric pair 11 of the group A of our classification. Chromosome polymorphism involving chromosome pairs No. 9, 12 and 13 is reported.
