The Organization of Drosophila melanogaster Histone Genes

Abstract

We have been interested in the two-dimensional restriction analysis of total Drosophila melanogaster DNA (Potter and Thomas 1978). These displays of restriction segments are prepared by terminally digesting genomic DNA with one restriction endonuclease, then fractionating the restriction segments with respect to length by electroelution into about 100 fractions. These primary segments are then redigested with a second endonuclease and electrophoresed on horizontal agarose slab gels. After drying and autoradiography, several thousands of bands can be resolved, many of which are only represented once per haploid genome. In contrast, a surprising number of segments have 10 to 100 times more label than expected for single-copy segments. They are seen as dense bands in one or two second-dimension channels or, alternatively, are seen as lines (i.e., secondary segments of defined length) that are cut from primary segments of highly variable length. These lines suggest the presence of numerous defined sequences, many...