Medicine and Healthcare

Medical Genetics:

     It is thought by some that the disease classification system will eventually be based on genetic evidence rather than symptoms and will change clinical practice from a routine of diagnosis and treatment to one of prediction and prevention.
     Drugs will be tailored for patients whose individual responses can be predicted by their genes; gene function and knowledge of molecular pathways that lead to disease will guide drug design (the field of pharmacogenomics). Together with new technologies, the human genome sequence will help to define many of the genes underlying susceptibility to various diseases.
     However, some people believe that although obtaining genetic information should be the first of many steps in understanding disease processes, multiple interactions between genes (and between genes and the environment) might prevent accurate analysis. These added levels of complexity could prevent the correlation of genotype with clinical phenotype, particularly for common multifactorial disorders. These factors may mean that the prediction ability of a genetic test could be less accurate than expected and the impact of the HGP might be limited by the fact that only a small proportion of the population has Mendelian (single gene inheritance) disorders.

     In light of these changes, medical staff - such as physicians - will need to take on new responsibilities. They will need to know the new classification of disease systems (likely to be different from that learnt in medical studies) and will need to understand the kinds of tests that are available, which patients each test is most applicable to and how to interpret the results. Not only this, but it is increasingly more necessary for staff to inform patients of the outcomes and options of being genetically diagnosed in a sensitive manner, since being "labelled" with a genetically inheritable disease can be distressing for some individuals.
     This is one of the reasons why genetic counselling is now so crucial in the medical industry. The specific training allows people to gain greater insight into the psychological aspects of genetic screening and diagnosis, and enables patients to give feedback on their being diagnosed in the form of counselling therapy. It will also be possible through genetic counselling to advise individuals on the possible lifestyle changes they may need to make, since environmental effects are equally important as genetic.

 

Gene Therapy:

     Once a disease gene has been identified, it can be used as a form of medicine against the disease. Gene therapy involves cloning the functional ("normal") gene and integrating it into the DNA of the defective cells that have the inactive allele of the gene. It can even be used as a form of vaccine by targeting for the immune cells of the body.
     However, gene therapy has currently had very little success in the medical industry, due to its low progress in clinical trials and this was especially in the case of Jesse Gelsinger - a boy who tried gene therapy for his ornithine transcarboxylase deficiency (OTCD) disease but died due to a severe immune response to the carrier molecule containing the functional gene. Some children also developed leukaemia as a result of gene therapy for their X-linked Severe Combined Immunodeficiency Disease (X-SCID).
     These cases forced authorities to place a ban in 2003 on gene therapy clinical trials using blood stem cell disorders in fear of the safety of the testers, but they are currently debating whether to continue using gene therapy trials for life-threatening diseases as perhaps the possible resulting "side-effect" illness is outweighed by the lengthened life span.

 

Cardiology:

     Taking cardiology as an example of a large medical field which deals with one of the highest mortality & morbidity rates in medicine, this can give insight into the applications of the HGP in a specific aspect of healthcare.

     The HGP has allowed the identification of numerous genes that contribute towards heart abnormalities such as cardiomyopathies, arrhythmic disorders, vascular diseases and inherited conditions. Prior to the completion of the human genome sequencing, the genetic strategies used to locate these genes were limited, but in the post-genomic era we can now use the HGP to specifically determine the gene locations using markers and other techniques.
     It is also possible to compare and contrast between disease risks of different gene mutations. For example, one gene mutation (e.g. the "myosin-binding protein C" gene) will give a lower risk of death in hypertrophic cardiomyopathy than another (such as the "beta-myosin heavy chain" gene).
     Clinical symptoms can also be diagnosed using the genotype rather than the phenotype, leading to more specific diagnoses of cardiac diseases. The fact that many of the cardiac diseases are similar means that the determination of the genotype will enable a much greater ability to distinguish one from another. This will also allow a "prevention is better than cure" (prognosis) approach in that those with an inherited gene but do not show symptoms can then take precautionary steps to alter their lifestyle in a risk-reducing manner.

     Gene therapy in cardiology is targeting genes that play a role in the strength of heart muscle contractions, such as those in the signalling mechanism or in the muscle tissue itself. It also aims to improve genes coding for proteins involved in cardiovascular disease, such as angiotensin, and even thought possible to convert one type of tissue into specific cardiac muscle. However, the latter is not likely since the electric conductivity needed to activate the heart muscle when the heart contracts is like no other tissue and this limits how successful this might be. The applications of these methods are also probably not going to be put forward until some time into the future, since issues with gene therapy have still not been eradicated.

 

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