Genetic Language is Abstract and Flexible

The awesome power that genetic engineering will one day place in our hands was foreshadowed recently by some experimenters at the University of Basel in Switzerland. Walter Gehring and his students were studying the effects of the eyeless gene in fruit flies. The gene is called eyeless because its absence causes flies to grow without eyes. The gene actually causes eyes to grow. Gehring and the students inserted the gene into various tissues of embryonic flies, and the embryos grew into flies with eyes sprouting from their legs or wings or antennas. The superfluous eyes were anatomically perfect. This gene somehow commands a whole army of several thousand subordinate genes to perform the miracle of creating an eye.

But this was only the first miracle. Gehring's group had previously discovered that the 'eyeless gene in fruit flies is chemically similar to a gene small-eye in mice and to a gene aniridia in humans. The absence of small-eye causes mice to grow with defective eyes, and the absence of aniridia causes blindness in human babies. The second miracle occurred when Gehring put the small-eye mouse gene into the leg of a fruit-fly embryo. The embryo grew into a fly with a perfect fruit-fly eye attached to its leg. So the identical smalleye gene is able to command the creation of a mouse eye in a mouse and the creation of a fruit-fly eye in a fruit fly. This shows an amazing flexibility in the power exercised by the gene. The basic design of a mouse eye is totally different from the design of a fruit-fly eye. Every detail in the anatomy of the two eyes is different. The mouse eye is like a human eye, with a retina and a lens, the lens focusing an optical image onto the retina. The fruit-fly eye is an array of hundreds of inde- pendent units, each detecting light from a particular direction but without any sharp focus. The experiment shows that the small-eye gene is not concerned with anatomical structure but with abstract function. The gene commands "Create an eye" in some abstract language that the mouse genome can translate into mouse anatomy and the fruit-fly genome can translate into fruit-fly anatomy. The language of the genes is demonstrated to be far more abstract and flexible than anybody had imagined before these experiments were done.