UC Irvine

Comparative screening of a library of cloned Drosophila DNA with polyadenylated mRNA from Drosophila adult head and adult body identified 20 cloned sequences expressed more abundantly in the tissues of the head than in other tissues. Quantitation using a "dot blot" hybridization assay demonstrated that the DNA sequences are expressed on adult head polysomes from 3 to 177 times more abundantly than on body polysomes, and their transcripts represent from 0.05 to 0.66% of the polyadenylated mRNA mass of the head. The steady-state nuclear RNA concentrations of four species were determined to be from 13 to 48 times greater in head nuclei than in body nuclei, an indication that their expression is controlled at least in part at the transcriptional level. The chromosomal locations of all 20 head-specific clones were identified by in situ mapping, and no distinct clustering was observed. However, four of the clones were shown by Southern and Northern blot analysis to contain multiple RNA coding sequences. The genes in these tightly clustered sets were observed to be expressed simultaneously in some cases and differently in others. © 1982.