Eulalee ThompsonTHE COMPLETE mapping of the human genome, though an esoteric issue for many, is a formidable development to further understand the disease process and to achieve a cure. Dr. Wayne McLaughlin, a scientist based at the University of the West Indies' Department of Basic Medical Sciences (Biochemistry Section) says this achievement will have implications for the future of health care in Jamaica and the rest of the world.
"The ultimate goal is to be able to replace a defective gene, essentially replacing the bad gene with the good gene. In Jamaica for example, sickle cell disease is common. This disease affects the ability of the red blood cells to transport oxygen. A change in a single amino acid results in the sickle cell anaemia. If the gene can be located, then by gene therapy, the normal gene can replace the defective gene. This will however, take some time, as gene transformation systems have to be developed," he said.
The area of drug designing should also benefit from the completed gene mapping. Dr. McLaughlin said drugs can be designed to target specific diseases and individuals. "Initially, such gene-targeted treatment will be expensive due mainly to development costs. Also, diseases that are researched for treatment may be those more common to developed countries. It will be a while before countries like Jamaica benefit from this new breakthrough," he cautioned.
Before the announced breakthrough last week, which was the identification of the total genetic make up of the human being, scientists had identified only a small percentage of genes in the body. Each person (except for identical twins) has a unique gene structure. There are between 60,000 and 100,000 genes in an individual which are inherited equally from both parents.
Dr. McLaughlin said every function in the body is controlled by a gene. He lists for example, the function of the production of digestive enzymes such as pepsin, or the production of insulin which is used to regulate the levels of blood glucose or the production of haemoglobin, which is used for carrying oxygen in red blood cells. But genes also determine gender and the colour of one's hair and eyes.
Genes are located on chromosomes (threadlike structures found in the nucleus of cells) and every cell contains chromosomes. Dr. McLaughlin explained that human beings carry 23 pairs of chromosomes that carry hundreds of thousands of codes that direct the cell's biosynthetic processes. One pair, X and Y determines the gender of a person. A female has two X chromosomes and a male has an X and Y chromosome.
He said chromosomes are comprised of DNA (deoxyribonucleic acid) and genes are found within the DNA and carry the instruction that directs the synthesis of proteins. The base of the DNA structure carries the genetic information and there are four bases called A for adenine, G for guanine, C for cytosine and T for thymine. It is the variation in the arrangement of the bases that gives different genetic instructions.
"In constructing a map of the human genome, scientists have essentially determined the arrangement of the bases (ACGT) in the DNA that are present in the chromosomes. This is an enormous feat since there are 23 pairs of chromosomes consisting of about 3.2 billion bases," he said.
