Ascientist shines ultraviolet light on a colony of blue colored bacteria. she then places colonies of the bacteria in separate petri dishes. after allowing the bacteria to replicate for several generations, the scientist observes that some of the dishes now contain colonies with purple and red colored bacteria. what can be concluded from this observation? a. asexual organisms will undergo genetic changes if placed in a petri dish. b. mutations lead to genetic variation in organisms that reproduce asexually. c. genetic changes are always harmful to organisms that reproduce asexually. d. organisms undergo mutations to become better suited to their environment.

Keeping in mind the life cycle of bacteriophages, consider the following problem: during the reproductive cycle of a temperate bacteriophage, the viral dna inserts into the bacterial chromosome where the resultant prophage behaves much like a trojan horse. it can remain quiescent, or it can become lytic and initiate a burst of progeny viruses. several operons maintain the prophage state by interacting with a repressor that keeps the lytic cycle in check. insults (ultraviolet light, for example) to the bacterial cell lead to a partial breakdown of the repressor, which in turn causes the production of enzymes involved in the lytic cycle. as stated in this simple form, would you consider this system of regulation to be operating under positive or negative control?