Patterns of Heredity and Human Genetics
Posted 3/16/00
Getting a New Pair of Genes
Hemophilia - a condition in which a person's blood does not clot - is a genetic disorder in which a single gene on the X chromosome does not work properly. When healthy,
this gene produces Factor IX, a protein that causes blood to clot when exposed to the open air. Without Factor IX, wounds will not heal properly. It is estimated that one in every 50
000 males suffer from hemophilia.
Throughout daily life, people are constantly suffering minor cuts and scrapes. Most people don't even realize it when it happens, and the blood automatically clots.
However, persons with hemophilia (known as hemophiliacs) can bleed to death from a mere scratch. The tiny wounds don't heal, and they experience what is known as "spontaneous bleeding."
While some medication is available for hemophiliacs, researchers are actively studying gene therapy as a way to treat hemophilia. Gene therapy is promising for this
ailment mainly because the disease is caused by a defect in a single gene. This makes it easier to treat than one that is caused by various genes on different chromosomes.
A new genetic treatment for hemophilia has been tested and shows success. The process uses two replacement genes to treat the defect in one. This one-two punch first
introduces a gene that instructs the body to manufacture Factor IX. A second gene is introduced to control production of Factor IX.
Lili Wang and Inder Verma of the Salk Institute in La Jolla, California, developed this treatment and tested it on dogs that had hemophilia. (Dogs develop hemophilia
exactly the way humans do - through a genetic disorder.) After being treated with this new therapy, all dogs began producing Factor IX. And, the dog that received the highest dose was
able to produce enough Factor IX to stop spontaneous bleeding.
This experiment occurred 10 months ago, and this dog is still healthy today. The success of this experiment has led Wang and Verma to push for the next step - to test
it in humans.
Activity
Use the Internet to learn more about Gene Therapy. With a partner in class, develop a timeline showing the history of gene therapy. Present your findings
to the class.
References
|
