NEET2013ZoologyMolecular Basis of InheritanceActual
In an inducible operon, the genes are:
Options
- Ausually not expressed unless a signal turns them "on".
- Busually expressed unless a signal turns them "off".
- Cnever expressed
- Dalways expressed
Correct answer
A. usually not expressed unless a signal turns them "on".
Step-by-step solution
When E . coli is exposed to both lactose and glucose, the organism first metabolise glucose and then temporarily cease to grow until the genes of lac operon become included to provide the ability to metabolise lactose. Allolactose is called an inducer because in its presence it turns on, or induces the expression of the lac genes. Related Theory When lactose is present outside the cell. it crosses the cell membrane and acts as an inducer of the operon. It does so once lactose is broken down to create allolactose. T