Chapter 16 - Regulation of Gene Expression - 16.3 - Viruses Regulate Their Gene Expression during the Reproductive Cycle - 16.3 Recap - Learning Outcomes - Page 348: 2

Cro and cl are two regulatory proteins that compete to control the expression of one another, as well as genes for viral lysis and lysogeny. Under ideal conditions, cI outcompetes Cro for DNA binding, pushing the bacteriophage into a lysogenic cycle. But under more dire conditions, cI is degraded and no longer represses transcription of the Cro gene. This occurs when the phages are raised in an area with low nutrients or are exposed to toxins or radiation. As a result, the bacteriophage enters the lytic cycle.

Cro and cl are two regulatory proteins that compete to control the expression of one another, as well as genes for viral lysis and lysogeny. Under ideal conditions, cI outcompetes Cro for DNA binding, pushing the bacteriophage into a lysogenic cycle. But under more dire conditions, cI is degraded and no longer represses transcription of the Cro gene. This occurs when the phages are raised in an area with low nutrients or are exposed to toxins or radiation. As a result, the bacteriophage enters the lytic cycle.