Analysis of cis-acting regulatory elements with reporter genes

Toolkit loci (such as hunchback, as described in the text) often contain multiple independent cis-acting regulatory elements that control gene expression in different places or at different times during development or both (for example, A, B, C, here). These elements are identified by their ability, when placed in cis to a reporter gene and inserted back into a host genome, to control the pattern, timing, or level, or all three, of reportergene expression. In this example, each element drives a different pattern of gene expression in a fly embryo. Most reporter genes encode enzymes or fluorescent proteins that can be easily visualized.