Springer Online Journal Archives 1860-2000
Abstract Non-LTR retrotransposons, also known as LINEs, transpose by reverse transcription of an RNA intermediate. Their mechanism of transposition is apparently different from that of retrotransposons and similar to that of proviruses of retroviruses. The I factor is responsible for the I-R system of hybrid dysgenesis inDrosophila melanogaster. Inducer strains contain several functional I factors whereas reactive strains do not. Transposition of I factors can be experimentally induced: they are stable in inducer strains, but transpose at high frequency in the germline of females, known as SF females, produced by crossing reactive females and inducer males. We have constructed an I element, calledIviP2, marked with thevermilion gene, the coding sequence of which was interrupted by an intron. Splicing of the intron can only occur in the transcript initiated from the I element promoter. Transposed copies expressing a wild-typevermilion phenotype were recovered in the germline of SF females in which I factors were actively transposing. This indicates thattrans-complementation of a defective I element, deficient for the second open reading frame, by functional I factors can occur in the germline of dysgenic females.
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