Dennis M. Sullivan, MD, MA (Ethics)
Completion of the Human Genome Project in 2003 provided a “rough draft” of the human genetic code, with more details added almost daily. Current research is aimed at two major goals: 1) predicting and diagnosing disease, and 2) medical treatments.1
There are deep ethical implications to all of this. The manipulation of our own nature may seem to break certain traditional limits. There is a sense of uneasiness about the process, and concerns about altering human nature itself. The purpose of this article is simply to provide conceptual clarity about these complex and often technical issues, without delving into the ethical arguments themselves.
DNA (deoxyribonucleic acid) is an information-carrying molecule found primarily in the nucleus of all human cells. It acts as a “blueprint” to direct protein synthesis in the human body, and thereby control development, growth, metabolism, gender, and a myriad of other traits that make each one of us unique. No two human beings have the same genetic code; even identical twins have slight variations.2 The entire blueprint for each individual is referred to as the human genome.
The DNA in a cell’s nucleus is arranged in a sequence of bases, called nucleotides, arranged in pairs (base pairs). Millions of DNA base pairs are coiled into cylindrical structures called chromosomes, located in each cell nucleus. Human beings have 23 pairs of chromosomes, for a total of 46. An individual packet of genetic information is called a gene. There are 20,000 to 25,000 genes in the human genome, located in various chromosomes.
Genetic sequencing uses a variety of sophisticated biochemical techniques to determine the exact order of base pairs in a given chromosome. Alterations in the normal sequence may result from mutations, caused by deletions, substitutions, or additions of one or more base pairs. Such mutations may have deleterious effects, leading either to genetically-based diseases or to an increased susceptibility to chronic illnesses such as diabetes, heart disease, and various cancers.
The ethical and philosophical issues surrounding new awareness of the human genome center on three core concerns: 1) privacy and confidentiality, 2) genetic testing, and 3) altering the genetic code through genetic therapies.3 In the area of privacy and confidentiality, the key issue is how scientists, physicians, employers, insurance companies, and other interested parties may ethically use an individual’s genetic information.
For example, the BRCA1 and BRCA2 genes confer a five-fold increase in lifetime risk of developing breast cancer in women with this mutation.4 Such information could potentially be used by health insurance companies to deny coverage to women who test positive for these markers, or at least to make their coverage more costly. The recently passed Genetic Information Nondiscrimination Act of 2008 makes such a move illegal, and makes discrimination in the workplace based on genetic traits also unlawful.5
Another concern in this age of increased genetic information is the idea of ownership. Who owns the information obtained from the sequencing of genes and other pieces of DNA? Who will have access to it? Can genes be patented in order to protect proprietary research protocols, drugs, and treatments arising from the information?
The second major domain for ethical concern is that of genetic testing. How reliable and useful is the information obtained, and for what will it be used? In the unborn, prenatal genetic screening may take place by amniocentesis, a sterile technique where a needle is passed directly into the amniotic cavity surrounding the fetus in the uterus. Cells found in the withdrawn fluid are then tested for genetic anomalies. This procedure cannot be performed before the twelfth week of pregnancy, and itself carries a 0.5% risk of miscarriage. Chorionic villus sampling is an alternative procedure involving a tissue sample obtained through a transcervical catheter and ultrasound guidance. This can be performed earlier than amniocentesis (about 8 weeks), but carries an increased risk of miscarriage (1-2%). Frequently, prenatal testing is used as a justification for induced abortion if certain genetic abnormalities are found, such as Down syndrome, Tay-Sachs disease, Duchenne muscular dystrophy, and sickle-cell disease.6
Genetic testing can also be performed at a much earlier stage in human development. Preimplantation Genetic Diagnosis (PGD) involves the testing of embryos produced through in vitro fertilization (IVF). A single cell is removed from 3 day-old embryos and analyzed for certain genetic markers. If a genetic abnormality is discovered, such embryos are usually discarded. Some writers have compared this practice to the historical movement known as eugenics, an early 20th century practice that involved controlled selective breeding to “improve” the “genetic fitness” of the human race.7
Genetic testing can also be performed in adults, usually for specific disorders known to stem from a single mutation of a known region of DNA. An example is Huntington’s disease, a progressive neurological disorder that afflicts persons in middle age. On the other hand, most diseases with a genetic component are multifactorial, meaning that both genetic and environmental factors influence disease susceptibility. For example, a large (and mostly unknown) number of genetic mutations leading to an increased susceptibility to heart disease, diabetes, and certain cancers, in addition to environmental influences, such as lifestyle and diet. Genetic testing raises the question: should genetic analysis be performed for disorders where no treatment is available?
A final concern is the new arena of genetic therapy. In order to treat a genetically-based disorder, the “correct” genetic sequence must be inserted into the nuclei of a person’s cells, to replace the abnormal or mutated gene. This is possible through the use of a delivery vehicle, referred to as a vector (usually a virus), to insert new genetic information into cells. An example will help make this idea more clear.
Cystic fibrosis is a genetic disorder caused by an abnormality in a transport protein for chloride. In the bronchial tubes of the lungs, this results in thickened secretions and continuous lung damage, leading to chronic illness and a greatly decreased life expectancy. Recent clinical trials have studied the use of a modified common cold virus (as a vector), to which the corrected gene has been inserted. Patients are infected with the modified virus, which inserts its DNA (including the corrected chloride transport gene) into the lungs. The bronchial tubes can then transport chloride ion normally, and symptoms improve. Unfortunately, the salutary effects are only temporary at present.8
The above is an example of a somatic cell gene therapy. This involves alteration of the genes of an affected individual, often only in a target organ or tissue. The modified cells are somatic cells, or non-reproductive cells. Even if the change could be made to last longer, the modified genome would not be transmitted to future offspring.
This is in contrast to germ-line gene therapy, which involves the alteration of germ-line cells (sperm cells or ova) of an individual, so that offspring are also affected by the change. In other words, the changed genetic characteristics would be passed on to subsequent generations. Some ethicists would draw a line here and outlaw germ-line treatments, with the idea that effects on future humanity are too difficult to predict.
The forgoing examples have focused on attempts to treat genetically-based diseases or disabilities. But some authors have suggested that genetic modifications be done for enhancement purposes. This idea would go beyond genetic therapy to actual “improvements” of human abilities and perhaps even human nature itself (e.g., correcting eyesight to greater than 20/20, improving memory, or even extending life beyond current limits). The treatment vs. enhancement debate will continue to be important as the technology progresses.
- Medicine and the New Genetics. 2008; http://www.ornl.gov/sci/techresources/Human_Genome/medicine/medicine.shtml. Accessed August 29. 2010.
- Bruder C, Piotrowski A, Gijsbers A, et al. Phenotypically Concordant and Discordant Monozygotic Twins Display Different DNA Copy-Number-Variation Profiles. American Journal of Human Genetics. 2008;82(3):763-771.
- Human Genome Project Information. [World Wide Web]. 2008; http://www.ornl.gov/sci/techresources/Human_Genome/elsi/elsi.shtml. Accessed August 29, 2010.
- BRCA1 and BRCA2: Cancer Risk and Genetic Testing. [World Wide Web]. 2010; http://www.cancer.gov/cancertopics/factsheet/risk/brca. Accessed August 28, 2010.
- Genetic Information Nondiscrimination Act of 2008. In: Congress, ed. Public Law 110–2332008.
- ‘Amniocentesis’ and ‘Chorionic Villus Sampling’. 2010; http://www.medicinenet.com/script/main/hp.asp. Accessed August 28, 2010.
- Image Archive on the American Eugenics Movement. 2010; http://www.eugenicsarchive.org/eugenics/. Accessed August 28, 2010.
- Learning About Cystic Fibrosis. 2010; http://www.genome.gov/10001213. Accessed August 28, 2010.