第 43 至 46 題為題組         Zebrafish, named for their characteristic stripes, have been a popular test subject for researchers. Onlya few centimeters in length, the fish breed easily in captivity, grow quickly, and their transparent bodymakes it easy to study their organs. Above all, they possess some amazing “self-healing” power. When partof their heart is removed, they can grow it back in a matter of weeks. When blinded, they can quickly regainthe ability to see.         Recent studies show that humans and zebrafish have the same major organs and share 70 percent ofthe genes. Moreover, 84 percent of human genes associated with disease find a counterpart in zebrafish.Scientists thus hope that understanding the self-healing mystery of the fish may one day allow humans toregenerate such organs as eyes, hearts, and spines.         Researchers at Vanderbilt University are particularly interested in zebrafish retina regeneration. Theyhave learned that damage of retina can cause blindness in zebrafish, yet it only takes about three to fourweeks before vision is restored. The structure and cell types of zebrafish retinas are almost identical to thoseof humans. If the process can be replicated in humans, it may give rise to new treatments for blindnesscaused by retinal damage.        In order to know exactly how zebrafish retina is regenerated, the team looked at the neurotransmittergamma-aminobutyric acid (GABA), a chemical messenger in the brain that reduces the activity of neurons.They found that lowering GABA levels in zebrafish can trigger retina regeneration, while a high level ofGABA concentration will suppress the regeneration process. This suggested that GABA plays an importantrole in the fish’s ability to regain their sight.         The team is beginning to test the GABA theory on mice. If that works, human trials will be next onthe agenda. If the research proves successful in humans, some of the nearly 40 million blind peopleworldwide may one day have a tiny, striped fish to thank.
【題組】43. What can we learn about zebrafish from the passage?
(A) How they should be studied in labs.
(B) Where they derive their regenerative ability.
(C) Why they share humans’ genetic code.
(D) What they may offer in medical advancements.