You have discovered an E. coli mutant that expresses a lac operon cap protein that is unable to bind cAMP. If you grew that mutant in glucose, lactose, IPTG, and glucose and lactose how would the galactosidase activity differ from an E. coli strain containing a functional lac operon? What […]

Assume you infected an E. coli culture with a virulent bacteriophage. Most of the cells lysed, but a few survived – 1×10^-4. You wonder where the resistant bacteria came from. Were they caused by the bacteriophage infection or did they already exist in the bacterial culture? Earlier, for a different […]

Viruses are typically not classified as true living organisms by biologists. Viruses have DNA or RNA and protein but are not able to replicate until they infect a host cell. Within the cell they must use the enzymes and molecular building blocks the host cell provides to replicate. Viruses cause […]

An atom exists in a gas molecule in the atmosphere. It passes by the nodules of a bean plant, where it is converted into ammonia and absorbed into the soil. Bacteria in the soil then convert the ammonia into a form that can be reabsorbed by the bean plant. When […]