Intercalary heterochromatin in Drosophila

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Abstract
Molecular and cytogenetic characteristics are given of a 2846 bp DNA sequence from the YDm12 clone, previously derived from the long arm of the Drosophila melanogaster Y chromosome. Sequence analysis revealed within it a 1176 bp fragment with 37 bp terminal inverted repeats, flanked by 6 bp direct repeats. This fragment (called “element 1360”) appeared to be A-T rich, and was saturated with short direct and inverted repeats of different degrees of homology and consensus sequences for transcription, potential Z-DNA transition and autonomous replication. After in situ hybridization to polytene chromosomes, the element 1360 exhibited variable, strain-specifics location in the euchromatic parts of the chromosome arms, but constant heavy labelling of the X chromosome region 12E1–2, autosomal regions 42B1–3, 52A1–2, 62A1–2, 75B, 82C1–3, chromosome bases, the chromocentre and numerous sites of chromosome 4. The possible role of element 1360 in heterochromatin organization is discussed.