The computer then detects that light and verifies that yes, the phytochrome turned on the gene.

FORBES: Cyborg Yeast Have Their Genes Controlled By Computer

The phytochrome can then be exposed to a different shade of red light to turn the gene off.

FORBES: Cyborg Yeast Have Their Genes Controlled By Computer

Exposure to light changes the shape of the phytochrome, which allows it to turn a gene on, so the gene will produce its particular protein.

FORBES: Cyborg Yeast Have Their Genes Controlled By Computer