Abstract
We have isolated, by molecular cloning, genes expressed differentially at the blastoderm stage of Drosophila melanogaster. Two of the blastoderm-differential genes are reexpressed at later stages, and map to single chromosomal loci 95C and 99E. The sequence at 99E is that encoding the myosin light chain 2. Two other blastoderm-differential sequences are members of multigene families (one of which is B104, or roo) and map to multiple dispersed chromosomal loci. A gastrula-differential sequence was found which maps to 71A. Most significantly, we have identified three genes encoding transcripts expressed uniquely at the blastoderm stage; these map to single chromosomal loci: 25D3, 75C, and 99D4-8. At least some of the blastoderm-differential and blastoderm-specific loci appear to be distinct from loci involved in embryonic pattern formation that have been identified in recent genetic "saturation" screens. The procedure of identifying genes specific to the blastoderm stage may thus allow the identification of genes, not previously identified by classical genetic techniques, that are involved in important embryonic processes.
