Gene expression is controlled in both prokaryotes and eukaryotes. This is important, because you wouldn't want all genes to be transcribed and translated at the same time. Watch the Brightstorm video, Gene Expression.
Prokaryotes turn genes on and off by controlling transcription. The major form of regulation in prokaryotes involves operons.
Eukaryotes regulate gene expression at several points, and transcription is controlled by regulatory DNA sequences.
Use the Gene Regulation Virtual Investigation to learn more about how the two types of cells regulate gene expression. Pay attention and take notes. There is a self check quiz on the last slide. You will be responsible for the information in this virtual investigation.
Other resources to use in understanding regulation of gene expression are linked below. Use these to help understand anything you're still unsure of.