Human color vision is based on three light-sensitive pigments. The isolation and sequencing of genomic and complementary DNA clones that encode the apoproteins of these three pigments are described. The deduced amino acid sequences show 41 +/- 1 percent identity with rhodopsin. The red and green pigments show 96 percent mutual identity but only 43 percent identity with the blue pigment. Green pigment genes vary in number among color-normal individuals and, together with a single red pigment gene, are proposed to reside in a head-to-tail tandem array within the X chromosome.

A method has been developed whereby a very large number of colonies of Escherichia coli carrying different hybrid plasmids can-be rapidly screened to determine which hybrid plasmids contain a specified DNA sequence or genes. The colonies to be screened are formed on nitrocellulose filters, and, after a reference set of these colonies has been prepared by replica plating, are lysed and their DNA is denature and fixed to the filter in situ. The resulting DNA-prints of the colonies are then hybridized'to a radioactive RNA Experimental Plan. Consider an experiment in which the Dm segments in a random set are individually inserted into a given E. coli plasmid. Transformation of E. coli by these hybrid plasmids to a phenotype conferred by genes in the parental plasmid will yield colonies that individually contain a single cloned Dm segment (1-3). If these segments are randomly distributed and exhibit a mean length of 10,000 base pairs, or 10 kb, then we expect that about one colony in 16,000 will contain a particular nonrepetitive D. melanogaster DNA sequence the length of a typical structural gene, i.e., 1-2 kb. Hence, the goal is to devise a screening procedure whereby one can rapidly determine which colony in thousands contains such a sequence.The' screening procedure that we have developed is designed to detect sequences that can hybridize with a given (1) and the desired bacteria are transferred to the filter surface either by spreading or using sterile toothpicks to obtain <7 colonies per cm2 after incubation of the filter-plate at 37°. The reference set is produced by replica plating of the colonies that develop on the filter to L-agar plates and is stored at 2-4°.

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In D. melanogaster a pulse of the steroid hormone ecdysone triggers the larval-to-adult metamorphosis, a complex process in which this hormone induces imaginal tissues to generate adult structures and larval tissues to degenerate. We show that the EcR gene encodes three ecdysone receptor isoforms (EcR-A, EcR-B1, and EcR-B2) that have common DNA- and hormone-binding domains but different N-terminal regions. We have used isoform-specific monoclonal antibodies to show that at the onset of metamorphosis different ecdysone target tissues express different isoform combinations in a manner consistent with the proposition that the different metamorphic responses of these tissues require different combinations of the EcR isoforms. We have also determined temporal developmental profiles of the EcR isoforms and their mRNAs in whole animals, showing that different isoforms predominate at different developmental stages that are marked by a pulse of ecdysone.