Chapter 4 - 6

06 Biology

Genetic Therapy

Genetic code provides the basis of most physical characteristics.

It determines one’s gender, eye color, hair color, and a myriad of other factors that make every person unique.

Just as a computer program gives specific instructions on how the computer should act, genetic codes contain instructions for all cellular activity.

In some instances, however, a person’s genetic code can be flawed.

A gene may undergo mutations for a number of reasons.

This can result in a genetic disease.

A genetic disease is so ingrained in a person’s genetic code (DNA) that it cannot be cured using traditional medical methods.

Doctors cannot simply prescribe medicine or perform surgery to repair genes.

Instead, the genetic structure must be manipulated directly.

Only with recent advances in genetic science have physicians been able to begin curing genetic diseases.

Doctors can now treat a number of genetic diseases that individuals may inherit from their parents.

The process, however, is difficult to master and continues to pose a number of problems.

Perhaps more than any other medical field genetic therapy remains truly experiment.

In order to alter a person’s genetic code, the particular gene causing the problem must first be identified.

By taking tissue samples and isolating a strand of DNA from a cell, scientists can compare an individual’s DNA to a normal genetic code.

After the mutated portion of the DNA has been discovered, scientists can go about engineering a genetic treatment to permanently fix the problem.

The process is not simple.

The body’s immune system is designed to identify DNA structures Besides those normally found in the body and destroy the cells containing them.

In order to bypass the immune system, scientists have to introduce the new genetic code using different methods.

The repair of a gene involves a device called a vector.

A vector can be any form of biological material that carries a genetic code.

Viruses are the most common vectors used, as they are pathogenic and easily spread throughout a person’s cellular structure.

Doctors manually manipulate the genetic makeup of a vector before the material is introduced into a patient’s body.

This is so that it will carry new, repaired DNA to the body.

If the vector is a virus, then the virus has been engineered so that it is harmless.

The vector is then placed inside an individual.

Vector transplants may take place ex vivo (externally) by removing a portion of the patient’s body.

This introduces the vector directly into the tissue and places it back into the body.

Alternatively, vectors may be implanted in vivo, whereby vector cells carrying the new DNA are injected directly into the patient’s body.

Transplants typically take place within the part of the body affected by the genetic disease.

For instance, a person with a genetic disease affecting the liver might have it removed in order to introduce the vector cells ex vivo before putting it back in the body.

Genetic therapy is not as simple as introducing a vector, however.

The body’s immune system is designed to detect cells with a genetic makeup unlike the DNA carried by the rest of the cells in the body.

Genetic therapy may be in vain if the body’s immune system attacks and kills the vector cells containing repaired DNA.

In 2006, a group of Italian researchers discovered a way to overcome this problem.

Their method allows doctors to manipulate another portion of the DNA strand.

This prevents the body’s immune system from identifying the unique genetic code.

As a result, vector cells can replicate in the body unhindered by the immune system.

The use of viral genes as vectors remains a source of concern for gene therapy.

If the body’s immune system has already been exposed to the virus used as a vector, it is more likely able to destroy cells containing the new DNA.

Additionally, introducing new DNA to a particular portion of the body can cause discomfort in the patient.

Moreover, there is always the possibility that the viral vector will recover its ability to cause disease inside the patient.

In this case, a genetic disease may be treated, but a new, potentially harmful disease may be introduced into the patient’s body.

Given the manipulation the disease may have undergone to prevent the body’s immune system from attacking the vector, it is possible that the immune system will be unable to fight the new disease.

In spite of these risks, a number of doctors are now using genetic therapy to treat patients.