Ribosomal Gene Reiteration in a Marsupial Species with an X-linked Nucleolar Organizer

The number of ribosomal cistrons in somatic cells of males and females of Macropus eugenii have been estimated using RNA/DNA hybridization in 70% (v/v) formam ide. The male has one X-linked active nucleolar organizer and the female two and while the number of ribosomal cistrons is variable between the four males examined (31-65 copies), it is substantially less than the number present in the three females (94-103 copies). There is, therefore, no evidence of dosage compensation by amplification.