The adjacent and divergently transcribed yp1 and yp2 genes of Drosophila were separated at a site that is 342 base pairs upstream of yp2 and 883 base pairs upstream of yp1. Each gene was separately used to transform Drosophila germ-line-producing flies with a single copy of the introduced gene. Transcripts from the introduced genes were found only in adult females. Thus, the introduced genes maintain the sex- and time-specific expression pattern of the endogenous yp genes. However, the pattern of tissue-specific expression differed among the two introduced genes and the endogenous genes. Transcripts from both of the endogenous genes are found in fat bodies and ovaries. In contrast, transcripts from the introduced yp1 gene are found only in fat bodies, and those from the introduced yp2 gene are found only in ovaries. Thus, each introduced DNA segment lacks at least one of the cis-acting elements required for the normal pattern of tissue-specific expression. These results indicate that the expression of a yp gene in different tissues is determined by different cis-acting elements.

Garabedian, M. J., Hung, M. C., & Wensink, P. C. (1985). Independent control elements that determine yolk protein gene expression in alternative Drosophila tissues. Proceedings of the National Academy of Sciences, 82(5), 1396–1400.