研究生科技英语阅读课后习题close原文

Is GM Food Safe To Eat ?

Traditional plant breeding involves crossing varietiesof the same species in w ays they could crossnaturally. For example, disease-resistant varieties of wh eat have been crossed with high-yield wheat to combine these properties. T his type of natural gene exchange is safe and fairly predictable.

Genetic engineering ( GE) involves exchanging genes between unrelated spe cies that cannotnaturally exchange genes with each other. GE can involve the exchange of genes betweenvastly different species— e.g. putting scor pion toxin genes into maize or fish antifreeze genes into tomatoes. It is po ssible that a scorpion toxin gene, even when it is in maize DNA1, will still g et the organism to produce scorpion toxin— but what other effects may i thave in this alien environment? We are already seeing this problem — addi ng human growth hormone genes to pigs certainly makes them grow — but i t also gives them arthritis andmakes them cross-eyed, which was entirely un predictable.

It will be obvious, for example, that the gene for human intelligence will n ot have the sameeffect if inserted into cabbage DNA as it had in human DNA — but what side-effect would ithave? In other words, is GM food2 safe to ? The answer is that nobody knows becauselong-term tests have not been carr ied out.

Companies wanting a GM product approved in the UK or USA are required to provide regulatorybodies with results of their own safety tests. Monsanto’s3 s oya beans were apparently fed tofish for 10 weeks before being approved. Th ere was no requirement for independent testing,for long-term testing, for te sting on humans or testing for specific dangers to children or allergic4 peopl e.

The current position of the UK Government is that"There is no evidence of l ong-term dangersfrom GM foods."In the US, the American Food and Drug Ad ministration5 is currently beingprosecuted for covering up research that sug gested possible risks from GM foods.

A consistent all-over tan may be impossible to achieve because some body areas are much more resistant to tanning than others, a study has found.

Researchers - funded by the Medical Research Council (MRC) - at the University of Edinburgh say the results explain why some holidaymakers find it so hard to achieve an even tan all over their body.

The findings, published in the journal Experimental Dermatology, show that the buttock is much more resistant to sunshine but surprisingly when it does go red it tans less well than other areas.

It was also found that people with no freckles tanned more easily than those without freckling.

The study represents the first time that the depth of a person's tan, and not just skin redness, has been quantified.

Scientists carried out the study to try and solve the puzzle of why different types of skin cancer tend to be found in different parts of the body, given that they are all caused by exposure to sunshine.