Nucleic Acids Research, 1981, Vol. 9, No. 19 4997-5010
© 1981
MOLECULAR BIOLOGY |
Coding region deletions associated with the major form of rDNA interruption in Drosophila melanogaster
Department of Biology, Yale University New Haven, CT 06511, USA
Received June 24, 1981. The nucleotide sequences at and around the termini of 5 kb type 1 inter-ruptions in three separate clones of D. melanogaster rDNA repeats have been determined, and have been compared with the sequence of the corresponding region of an insertion-free rDNA repeat. All three interrupted rDNA repeats contain a small deletion of 28S rRNA coding material at the left coding/insertion sequence junction. A second deletion was found in one of the three clones, and other aberrations were suggested by the results of restriction enzyme digestions of unfractionated rDNA. The termini of 5 kb type 1 rDNA insertions in D. melanogaster were also compared with the corresponding regions of 28S rDNA interruptions in D. virilis: the insertion site is identical in the two species, but the termini of the two species' interruptions show no homology. I sequenced a 1.1 kb region of the 5 kb type 1 D. melanogaster rDNA interruption that covers the sequences of the 1 kb and 0.5 kb insertions. There is 98% homology between the rightmost 1 kb of the 5 kb interruption and the sequences of the shorter insertions. Data suggest that Drosophila rDNA interruptions arose as a transposable element, and that divergence has included length alterations generated by unequal crossing over.