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NOVA scienceNOW: RNAi

Program Overview

An accidental finding related to an experiment with purple petunias led to the discovery of RNA interference (RNAi). RNAi is a cellular mechanism that protects the cell from some types of viruses and from certain forms of genetic material that could harm the cell. The program explains how RNAi works and why it could become a valuable tool in learning about how genes influence growth and development and in curing or treating certain diseases.

This NOVA scienceNOW segment:

• reviews how proteins are made and notes the central role RNA plays in protein synthesis.

• relates how geneticist Rich Jorgenson tried to make a petunia with an especially deep purple hue by injecting petunias with additional genes for purple pigment (in the form of double-stranded RNA). Surprisingly, he got white flowers. This unexpected result led researchers to the discovery of RNAi.

• explains that RNAi works as a defense system against viral RNA. The genes the geneticist added to make more purple pigment in the petunia caused the plant to respond as though it had been infected with a virus, triggering an RNAi response. As a result, the plant stopped making pigment, which resulted in the production of only unpigmented (i.e., white) flowers.

• shows RNAi as a treatment for macular degeneration and mentions other diseases, such as arthritis, cancer, and Lou Gehrig's disease, that may potentially be treated with RNAi therapies.

• ventures that RNAi may be very important to the Human Genome project by potentially giving scientists the ability to turn off genes one at a time, providing insight into the function of individual genes.

Taping Rights: Can be used up to one year after the program is taped off the air.