Drosophila exhibits a wide variety of body and wing markings. A general example is the occurrence of a black spot near the tip of the wing in males. For the development of black spot, enzymes are needed to synthesize melanin, which can be better studied in Drosophila melanogaster. One gene is termed as yellow, as the mutation in the gene produce darkly pigmented areas of the body to look yellowish or tan. Species have black spots in wings due to the high levels of yellow protein expressed in wing cells and species without spots indicates the low levels of yellow protein.
The yellow gene is controlled by selection of separate cis-acting regulatory sequences that direct gene transcription in various tissues. The regulatory sequences involve those controlling transcription in the larval mouth parts, pupal thorax and abdomen, and the growing wing blade. It is revealed that, the wing blade cis-acting regulatory element from unspotted species make low level expression of a reporter gene across the wing blade. Whereas, the resultant element from spotted species like Drosophila biarmipes or Drosophila elegans makes a high level of reporter expression in the spot at the tip of the wing. The studies explain the alterations in sequence and function of a cis-acting regulatory element are answerable for the modification in yellow regulation and play a role to the origin of the wing spot.