Genetic engineering has reached the point where scientists have identified an “intelligence gene” in mice. The “smart mouse”was engineered by a team of scientists who took a gene for creating a substance called NR2B and spliced it into the DNA of an ordinary mouse. NR2B works to increase the “plasticity” of the brain―that is, the ability to link and reinforce similar memories so that learning takes place.   It may well become possible to modify a part of the genetic chemistry that accounts for human intelligence. This development has many people worried. They ask whether it is ethical to interfere in natural processes in this fashion and if the drawbacks may outweigh the advantages. Dr. Robert Malcnka of Stanford University comments, “If your memory improves too much, you may not be a happier person. I'm thinking of rape victims and soldiers coming back from war. There’s a reason the brain has evolved to forget certain things.”   Is genetic modification any different from plastic surgery or prenatal screening for inherited diseases? Some people argue that genetic engineering in areas including intelligence, appearance, and physiology will erase the differences between people that help create a healthy society. “We run the risk,” says Elizabeth Bounds, an ethicist at Emory University, “of shaping a much more homogeneous community around certain dominant values. As someone who morally values diversity, I find this alarming.”   Science continues to unravel the mysteries of how living organisms work. Having designed a “better” mouse, we may soon be able to manipulate the basic building blocks of a human being to create smarter, healthier people. One big question remains: Have we thought enough about the consequences of such genetic modification?