Mantle plumes are areas of hot, upwelling mantle and hot spots develops above these plumes as noted in the map above. magma generated by the hot spot rises through the rigid plates of the lithosphere and produces active volcanoes at the earth's surface. as oceanic volcanoes move away from the hot spot, they cool and subside, producing islands, atolls, and seamounts. as the magma cools in the water it forms rocks

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?