With lactose in the cell, lactose binds to the repressor. This causes a structural change in the repressor and it loses its affinity for the operator. Thus RNA polymerase can then bind to the promoter and transcribe the structural genes. In this system lactose acts as an effector molecule.his decrease in the complex inactivates the promoter, and the lac operon is turned off. Because the CAP-cAMP complex is needed for transcription, the complex exerts a positive control over the expression of the lac operon. Copyright Â© 1997.
Gangrene is not a contagious disease. It is a condition in which living tissue (e.g., skin, muscle, or bone) begins to decay and die because blood flow (and oxygen) to an area is blocked or because harmful bacteria invade the body's tissues after entering through a wound or sore.Gangrene most commonly affects the feet, toes, hands, and fingers.ry gangrene. Dry gangrene is the most common form of gangrene, and it occurs most frequently in the feet of people with diabetes * . Dry gangrene results from the gradual loss of blood supply to a part of the body.
The Story of Balto. On January 20, 1925 Nome sent out an urgent telegraph message out. It was calling for antitoxin. Nome's doctor had diagnosed cases of diptheria to many people in the town. Diptheria is a contagious disease that affects the thorat and lungs.