Gene Therapy

INTRODUCTION TO GENETICS

All living organisms are made up of cells. These cells have various functions in the body. A series of coded instructions are inscribed in its nucleus to coordinate its operations. The cell continuously reads and interprets instructions to carry out its functions. These instructions are called genes. Genes are elements of hereditary elements that a transferred from parents to offspring during reproduction and determine the inherited traits of the offspring (Romanuik, 2004). They are composed of deoxyribonucleic acid (DNA) that can be passed down and inherited from one generation to the next. DNA is a sequence of nucleotide bases, whose sequences carry the information required for constructing proteins which is critical for determining the properties of an organism. But how is it, exactly, that a gene is able to carry out all these functions?

Genetics is defined as the study of genes, how genes produce characteristics and how the characteristics are inherited (Hartl & Jones, 2005). Genetics involves studies on how cell's genetic material affects what goes on inside our body. There are several researches going on in the field of genetics to understand and manipulate our genes in order to improve health conditions. One of the many fields in Genetics involved in improving health conditions through gene manipulation is gene therapy. It would be discussed in detail in this paper.

Introduction to Gene Therapy

Gene therapy is a rapidly growing and promising field of medical research that involves the use of genes as medicine to fight against diseases and also prevent the development of diseases. This procedure does not involve the use of any form of medicine in terms of drugs and surgery. Gene therapy is defined as the transfer of therapeutic genes into specific cells of an individual in order to repair a faulty or absent gene which is responsible for the disease (Centre for Genetics Education, 2004; Hecht 2004). It could be simply explained as the introduction of a "healthy" gene into a person who has a disease caused by an "unhealthy" gene.

Since the early 1970's, scientists have known how to manipulate the structure of genes in the laboratory through a process known as gene splicing (Hunt, 2002). It involves removing a fragment of DNA containing genetic sequences desired and then inserting it into the DNA of another gene. The result is called a recombinant DNA (rDNA) and the process is known as genetic engineering (Hunt, 2002)

Offspring look like their parents because of the genes given to them from their parents. These genes contain DNA that carry information required for the formation of proteins, which provide the structural components of cells and tissues as well as enzymes for essential biochemical reactions. However, if the DNA is damaged or altered, necessary proteins may not be made which would result in abnormal genes that have the possibility of causing diseases.

To reverse diseases caused by genetic damage or altering, several approaches are used by researchers in correcting abnormal genes in an individual. Usually, a mutated or abnormal gene which has a potential of causing diseases is replaced by a "healthy" gene. A normal DNA is isolated and carried inside a vector, a carrier molecule usually made from a virus into the cells containing abnormal genes (Human Genome Program, 2005). Hopefully, the vector unloads the DNA into the cells of the abnormal genes which would produce the missing proteins and rectify the abnormality of the cell (Refer to fig. 1).

Presently, Gene therapy is conducted through clinical trials. According to Centre for Genetics Education (2005), there are over 600 clinical gene therapy trials initiated or approved worldwide (Refer to Table 2). Many questions surround the use of genes as a treatment for diseases. Some people including scientists are concerned about the side effects that may result if the transferred genes do not perform the right duties. Others fear that gene therapy is a way of controlling the natural development of humans in areas such intelligence and appearance. However, Gene therapy remains a promising treatment for several presently incurable diseases such as cancer, AIDS and other viral infections.

History of Human Gene Therapy

Over the past decades, gene therapy has undergone a lot of progress by researchers to enhance its effects on cells and organs in living animals, including humans. This brief history provides some highlights in the progress in the area of gene therapy.

In 1953, James Watson and Francis Crick announced their discovery of a double helix structure called DNA that contains the genetic information of living organisms in an article in Nature magazine.

In the early 1970s, scientists proposed "gene surgery" for treating inherited diseases caused by faulty genes. The idea was to take out the disease-causing gene and surgically implant a gene that functioned properly. Although sound in theory, scientists, then and now, lack the biological knowledge or technical expertise needed to perform such a precise surgery in the human body (Hunt, 2002).

In 1980, Dr. Martin Cline conducted the first unapproved and unauthorized gene therapy procedure. He conducted an rDNA transfer into the bone marrow cells of two patients with hereditary blood disorders (Vargo, 2003). This generated ethical concerns that resulted in a lot of calls for reviews from several organizations such as National Council of Churches, Synagogue Council of America, and the United States Catholic Conference. Dr. Cline suffered grave consequences for his over exuberance. He was forced to resign his department chairmanship at University of California Los Angeles (UCLA) and lost several research grants.

In 1989, Dr. French Anderson, Eli Gilboa and Dr. Michael Blaese won approval from National Institutes of Health (NIH) advisory panel to conduct a test that would transfer bacterial genes into immune cells of terminal cancer patients (Vargo, 2003). The test paved the way for dozens of gene-therapy efforts.

In 1990, the US federal government approved the first disease for gene therapy. The disease is the adenosine deaminase (ADA) deficiency that causes its affected patients to have a severely weakened immune system due to the lack of the ADA enzyme (Vargo, 2003)

In September 1990, Dr. French Anderson and Michael Blaese of the National Institute of Heath (NIH) performed the world's first human gene therapy experiment on a 4 year old girl named Ashanti DeSilva. She inherited a defective gene from both parents and suffered from ADA deficiency. The scientists

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