The transposable element, Tam 3, gives rise to large-scale chromosomal rearrangements at a low frequency, when it is inserted at the nivea locus of Antirrhinum majus. Some deletions that result from imprecise excision of Tam 3 provide an allelic series for functional analysis of the nivea gene promoter. Rearrangements involving deletion, dispersion and inverted duplication of flanking sequences, where Tam 3 remains in situ, have also been identified. These rearrangements have been mapped at the molecular level, and the behaviour of Tam 3 following rearrangement has been observed. It is clear that Tam 3 has enormous potential to restructure chromosomes through successive rounds of large-scale rearrangements.
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