Nucleotide sequences at the boundaries between gene and insertion regions in the rDNA of Drosophila melanogaster

AUTOR(ES)

Dawid, Igor B.

RESUMO

Ribosomal RNA genes interrupted by type 1 insertions of 1 kb and 0.5 kb have been sequenced through the insertion region and compared with an uninterrupted gene. The 0.5 kb insertion is flanked by a duplication of a 14 bp segment that is present once in the uninterrupted gene; the 1 kb insertion is flanked by a duplication of 11 of these 14 bp. Short insertions are identical in their entire length to downstream regions of long insertions. No internal repeats occur in the insertion. The presence of target site duplications suggests that type 1 insertions arose by the introduction of transposable elements into rDNA. Short sequence homologies between the upstream ends of the insertions and the 28S′ boundaries of the rRNA coding region suggest that short type 1 insertions may have arisen by recombination from longer insertions.

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