DNA-bound protein. Computer graphic of a tramtrack protein (two zinc-finger peptide, yellow) binding to a DNA (deoxyribonucleic acid, red and blue) molecule. The grey spheres are the two zinc ions in the peptide. Tramtrack proteins regulate the transcription of fruit fly (Drosophila sp.) DNA, a stage in the production of proteins from the DNA-coded instructions. A zinc finger is a type of DNA-binding domain. It is found in a wide range of DNA-binding regulatory proteins. Zinc fingers afford the protein a purchase on the DNA by projecting a precise arrangement of side chains into the helical DNA molecule. Fruit flies are used extensively in genetic research.