Genes

Gene therapy is a potentially experimental technique that uses genes to treat or prevent disease. In the future, this technique may allow doctors to treat a disorder by inserting a gene into a patient's cells instead of using drugs or surgery. Researchers are testing several approaches to gene therapy, including:

* Replacing a mutated gene that causes disease with a healthy copy of the gene.

* Deactivating a mutated gene that is functioning improperly.

* Introducing a new gene into the body to help fight a disease.

Each of us carries about half a dozen defective genes. Most of us do not suffer any harmful effects from our defective genes because we carry two copies of nearly all genes, one derived from our mother and the other from our father. The only exceptions to this rule are the genes found on the male sex chromosomes. Males have one X and one Y chromosome, the former from the mother and the later from the father, so each cell has only one copy of the genes on these chromosomes. In the majority of cases, one normal gene is sufficient to avoid all the symptoms of disease. If the potentially harmful gene is recessive, then its normal counterpart will carry out all the tasks assigned to both. Only if we inherit from our parents two copies of the same recessive gene will a disease develop. On the other hand, if the gene is dominant, it alone can produce the disease, even if its counterpart is normal.

Many medical conditions result from flaws, or mutations, in one or more of a person's genes. Mutations cause the protein encoded by that gene to malfunction. When a protein malfunctions, cells that rely on that protein's function can't behave normally, causing problems for whole tissues or organs. Medical conditions related to gene mutations are called genetic disorders.

There is a project currently going on called the Human Genome Project.

This international project is mapping a complete and accurate DNA sequence representing the genetic blueprint and evolutionary history of the human species. The construction of this genetic map is made possible through cooperative efforts of an international consortium of scientists who provide equal, full and unrestricted access to the data for the advancement of biology and human health. In less than