The dilution streaking technique can take a bit of practice to master. which of the following represent sources of error that would likely result in failure to obtain isolated colonies? choose one or more:

a. forgetting to sterilize the loop prior to obtaining the inoculum
b. flaming the loop immediately after obtaining the bacterial sample
c. forgetting to flame the loop before streaking sequential sections of the plate
d, allowing the loop to cool for too long before proceeding d
e. not creating a small section of overlap across sequential sections

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?