Please put the verbs in brackets into the appropriate form, making any necessary changes. Type your answers in the space provided.
1. By ................. (enhance) the function of a single protein, Howard Hughes Medical Institute researchers ................. (produce) a “marathon mouse” with altered muscle composition and enough physical endurance to run twice as far as normal mice. Mice with the enhanced protein also showed an innate resistance to weight gain, even when ................. (feed) a high-fat diet that caused normal mice ................. (become) obese.
According to the researchers, their finding ................. ( offer) important insights into the machinery that powers muscle development and the physiological changes produced by exercise. The finding also suggests a route to designing drugs that enhance muscle development and mimic all the benefits of exercise. The researchers said such drugs could aid patients whose debilitating diseases prevent them from ................. (exercise). The researchers recognize that such drugs - already ................. (test) by pharmaceutical companies - could be abused as a way to enhance athletic performance.
In their studies, the researchers ................. (explore) the effects of altering the gene for a protein called PPAR-delta — a master regulator of numerous genes — to enhance that protein's activity. According to Evans, they................. ( not/expect) the profound and far-reaching physiological effects of this single genetic alteration.
“In previous work, we had shown that in various tissues, particularly adipose tissues, activating PPAR-delta increased fat burning and, as a result, decreased fat-tissue mass,” said Evans. “Going into this experiment, the possibility of an effect on muscle fibers was not on our radar screen.”