1. a scientific is a statement that describes what scientists expect to happen every time under a particular set of conditions 2. when only one variable is manipulated at a time, an experiment is conducted.

3. the factor that can change in an experiment is called an

4. the variable is the only variable that is purposely changed to test a hypothesis

Which statement about inheritance is true? o girls get most of their traits from their moms, boys get most of their traits from their dads. o male offspring will always have an x-linked genetic disease if the mom is a carrier o fathers always determine the gender of the offspring in humans. o males never have y chromosomes.

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?

Ronald wants to see if a new shower cleaner works better in removing soap than his old cleaner. he uses the new cleaner on one half of the shower tiles and his old cleaner on the other half. identify the independent and dependent variables in this experiment. enter your answer in the space provided.