Choosing from the Genetic Menu

­The idea that we could one day manipulate the genes of humans should not surprise us. Scientists have been altering animal genes for years. Goats and cows have been manipulated so that they produce more milk or more proteins in their milk. Mice have ­been injected with genes that may cause Alzheimer's Disease in an effort to find a cure. Jellyfish genes have been injected into monkeys, which are in the same class of animals as humans, to show that genes could be inserted into a monkey genome.

One of the more interesting transgenic animals was created by injecting a spider gene into a goat's genome. Spider silk is very strong and, if produced in enough quantity, could create a very powerful type of body armor. And while spiders don't make enough silk to produce this super body armor, scientists discovered that spider silk is a protein similar to goat milk. When the spider gene is inserted into a goat, the goat produces a protein that is identical to that found in spider silk. This protein is extracted from the goat's milk to produce silk fibers, called BioSteel, which is used to make bulletproof vests.

Photo courtesy Nexia Biotechnologies Spider genes being injected into a goat's egg to produce a transgenic goat

So it is already possible to alter the genetic properties of living animals, some of whom have genetic makeups similar to that of humans. It's only a small leap from here to tampering with human genetics. Humans could be genetically altered to jump higher, see farther, hear better or run faster. Before these super humans can be created, though, we have to learn more about the human genetic code.

One method that could soon be used to manipulate human genetics is called germline gene therapy, and would involve adding an additional step to PGD. Beyond just screening embryos, germline therapy would actually add new genes to the cells. It's possible that almost any trait could be added to an embryo to create a tailor-made child.

Germline therapy, which is already being performed on animals, means manipulating genes of the sperm, egg or early embryo. The name germline comes from germinal cells, which are our reproductive cells. Genetic changes to these cells may not show up in the animal that results from the embryo, but instead show up in later generations.

As more is found out about the human genome and how are genes actually function, we will have to begin to face the possibility of made-to-order children. However, that time is still decades away.