共用题干 第二篇Are These Food Safe to Eat?Traditionally,in plant breeding,there are crossing varieties of the same species in ways they could cross naturally.For example,disease-resistant varieties of wheat have been crossed with highyield wheat to combine these properties.This type of natural gene exchange is safe and fairly predictable.Genetic engineering(G E)makes it possible to exchange genes between unrelated species that cannot exchange genes with each other in a natural way.GE can involve the exchange of genes be-tween vastly different species一e.g. putting scorpion toxin genes into maize or fish antifreeze genes into tomatoes.It is possible that a scorpion toxin gene,even when it is in maize DNA,will still get the organism to produce scorpion toxin一but what other effects may it have in this alien environment? We have already realized this problem一adding human growth hormone genes to pigs certainly makes them grow一but it also gives them arthritis and makes them cross-eyed,which was entirely out of expectation.It won't be difficult to find out,for example,that the gene for human intelligence will not have the same effect if it is inserted into cabbage DNA as it had in human DNA一but what side-effect would it have?In other words,is genetically modified(GM)food safe to eat?The answer is that no-body knows because long-term tests have not been carried out.Those companies who want a GM product approved in the UK or USA are required to provide regulatory bodies with results of their own safety tests.Monsanto's soya beans were apparently fed to fish for 10 weeks before being approved.There was no requirement for independent testing,for longterm testing,for testing on humans or testing for specific dangers to children or allergic people.The present opinion of the British Government is that"There is no evidence of long-term dangers from GM foods."In the US,the American Food and Drug Administration is now being prosecuted for covering up research that suggested possible risks from GM foods. Which type of natural gene exchange is safe and fairly predictable?
A.Adding human growth hormone genes to pigs. B.Natural gene exchange in traditional plant breeding. C.Inserting fish antifreeze genes into tomatoes. D.Putting scorpion toxin genes into maize.正确答案B
