Genetic engineering(GE)involves exchanging genes between unrelated species that cannot naturally exchange genes with each other.GE can involve the exchange of genes between vastly different species――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――but what other effects may it have in this alien environment?We are already seeing this problem――adding human growth hormone genes to pigs certainly makes them grow――but it also gives them arthritis and makes them cross-eyed，which was entirely unpredictable.

　It will be obvious ，for example
，that the gene for human intelligence will not have the same effect if inserted into cabbage DNA as it had in human DNA――but what side-effect would it have?In othe