A get retardation assay can be used to determine if a protein bids to a segment of DNA. When a segment of DNA is bound by a protein. Its mobility will be retarded, and the DNA band will appear higher in the gel. In the gel retardation assay shown here, a cloned gene fragment that is 750 bp in length contains a regulatory element that is recognized by a trascripion factor called protein X. Previous experiments have shown that the presence of hormone X result in transcriptional activation by protein X. The results of a gel retardation assay are shown here.

Explain the action of homone X.

2 3 4 Lane 1. No additions Lane 2. Plus hormone X Lane 3. Plus protein X Lane 4. Plus protein X and 750 bp hormone X