Drosophila melanogaster has different ribosomal RNA sequences on S and Y chromosomes. |
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Authors: | T Yagura M Yagura M Muramatsu |
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Affiliation: | Department of Biochemistry, Cancer Institute Japanese Foundation for Cancer Research Kami-Ikebukuro, Toshima-ku, Tokyo, Japan |
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Abstract: | The primary structures of ribosomal RNAs transcribed from the nucleolus organizers on X and Y chromosomes of Drosophila melanogaster were compared by RNase T1 fingerprints made with two different systems; i.e. homochromatography on DEAE-cellulose, and polyethyleneimine-cellulose thin-layer chromatography.Ribosomal RNA derived from the X-linked nucleolus organizer was obtained from a strain producing only female larvae and ribosomal RNA derived from the Y-linked nucleolus organizer was isolated from a mutant lacking the X-linked nucleolus organizer.No difference was detected between the fingerprints of 28 S RNA from these animals.In 18 S RNA, however, one oligonucleotide showed a remarkable difference in mobility. The structure of the X-linked organizer-specific oligonucleotide was 5′ U-C-U-U-U-U-U-U-C-C-U-A-U-G 3′, and that of the Y-linked organizer-specific oligonucleotide was 5′ U-C-U-C-U-U-U-U-C-C-U-A-U-G 3′, indicating one base substitution (U á3 C) between them.The absence of 5′-temninal phosphate in this oligonucleotide and available sequence data also suggest that these oligonucleotides did not come from either the 5′ or 3′ terminus of 18 S RNA.D. simulans, whose Y chromosome has no nucleolus organizer (Ritossa &; Atwood, 1966), showed an 18 S RNA fingerprint having only the X-linked organizer-specific oligonucleotide.We conclude from these results that in Drosophila the ribosomal RNA gene sequences are different for the two nucleolus organizers located on the X and Y chromosomes. The implications of those findings concerning the parallel evolution of these genes are discussed. |
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