Gene therapy carries the excitement of a cure-all for many diseases and the promise of a type of medical treatment most of us would never imagine possible. With its potential to eliminate and prevent hereditary diseases such as cystic fibrosis and hemophilia and its use as a possible cure for heart disease, AIDS, and cancer, gene therapy is a potential medical miracle-worker.

But what about gene therapy for children? There's a fair amount of risk involved in trials of this kind of  AIDS therapy, and to date, only kids who are seriously ill or have illnesses incurable by conventional means have been involved in clinical trials using gene therapy.

For those with serious illnesses that aren't responsive to conventional therapies, however, gene  AIDS therapy may soon offer hope that didn't exist just a short time ago.

What Are Genes?
Our genes are part of what makes us unique. Inherited from our parents, they determine our physical traits — like the color of our eyes and the color and texture of our hair. They also determine things like whether babies will be male or female, the amount of oxygen blood can carry, and IQ.

Genes are composed of strands of a molecule called DNA and are located in single file within the chromosomes. The genetic message is encoded by the building blocks of the DNA, which are called nucleotides. Approximately 3 billion pairs of nucleotides are in the chromosomes of a human cell, and each person's genetic makeup has a unique sequence of nucleotides. This is mainly what makes us different from one another.

Scientists believe that every human has about 25, 000 genes per cell. A mutation, or change, in any one of these genes can result in a disease, physical disability, or shortened life span. These mutations can be passed from one generation to another, inherited just like a mother's red hair or a father's brown eyes. Mutations also can occur spontaneously in some cases, without having been passed on by a parent. With gene therapy, the treatment or elimination of inherited diseases or physical conditions due to these mutations could become a reality.

Gene therapy involves the manipulation of genes to fight or prevent diseases. Put simply, it introduces a "good" gene into a person who has a disease caused by a "bad" gene.

Two Types of Gene Therapy
The two forms of gene therapy are:

Somatic gene therapy involves introducing a "good" gene into targeted cells to treat the patient — but not the patient's future children because these genes do not get passed along to offspring. In other words, even though some of the patient's genes may be altered to treat a disease, it won't change the chance that the disease will be passed on to the patient's children. This is the more common form of gene therapy being done.
Germline gene therapy involves modifying the genes in egg or sperm cells, which will then pass any genetic changes to future generations. In experimenting with this type of therapy, scientists injected fragments of DNA into fertilized mouse eggs. The mice grew into adults and their offspring had the new gene. Scientists found that certain growth and fertility problems could be corrected with this therapy, which led them to think that the same could be true for humans. However, although it has potential for preventing inherited disease, this type of therapy is controversial and very little research is being done in this area, both for technical and ethical reasons.