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Decoding disease

How knowing what we're made of is changing how we live

By MELISSA MARES
The diseases usually thought of as "genetic" are rare--Huntington's disease, cystic fibrosis and Tay-Sachs disease, among others. Although these diseases afflict a relatively small group of people, they make up a frightening group. As scientists and doctors have worked toward decoding and understanding the human genome, they have learned that these formidable illnesses are not the only ones that have a genetic link. 

"These diseases are ones where grandma had it, mom had it, I got it, and I will pass it on to my daughter," explains Dr. Rex Chisholm, director of the Center for Genetic Medicine and of the Biomedical Informatics Center at Northwestern University's Feinberg School of Medicine. "Obesity, heart disease, cancer--these are [the diseases] we worry about, and lots of people have them. They have a genetic component, but it's not strictly driven by that."

Issues often associated with genetic research, such as cloning and the fear that the public will start wanting "designer babies," are dramatic and often get a lot of attention.

However, Chisholm and others say that the most important aspect of genomic research is that doctors are becoming better able to diagnose and treat illness. With this new information, though, comes the responsibility to consider legal and ethical issues that the world has never before faced. 

The most basic discussion of genetics requires a bit of background information. All of the genetic material in human genes is known as the human genome. Humans have 23 pairs of chromosomes, and contained within these are between 20,000 and 25,000 genes.  Each chromosome is made up of two coiled strands of DNA--molecules that are made up of a string of bases (adenine, cytosine, guanine and thymine).  

This DNA is the foundation for all of the similarity and diversity among human beings throughout the world. 

"One letter of every 1,000 in our sequence will be different," says Chisholm. "There are three billion in the string, which makes three million differences between each of us."

The U.S. Human Genome Project began in 1990 and was coordinated by the U.S. Department of Energy and the National Institutes of Health. The goals of this initiative were to identify all of the genes in human DNA, and the Human Genome Project's official completion date was in April of 2003, when the journals Science and Nature published the project's results. On June 26, 2000, the Human Genome Project held a press conference to announce that a draft of the sequencing of the genome was complete. 

Though scientists have learned an extraordinary amount about the connection between genetic makeup and disease, there is still a great deal of research and work to be done. 

While the sequencing of the human genome is complete, scientists still do not know what many of the genes actually do.  Chisholm uses a textbook on theoretical physics as an example: in that text is the explanation of physics, but being able to read the book is not the same as understanding the ideas the words describe. Chisholm emphasizes that as much as we have learned about the human genome, there is more that we don't know than that we do know. 

"In a yeast cell, which has been very well studied, we still don't know what a quarter of the genes do," Chisholm says. "In a human, who has 22,000 to 24,000 genes, there's one-half to one-third of those genes that we don't know what they do."

For this reason, it remains extremely important for people to know their family health history and share it with their doctors. The more health information a patient can give to their doctor about their parents and grandparents, the better.

Dr. Nancy Wexler is the Higgins Professor of Neuropsychology at Columbia University and the president of the Hereditary Disease Foundation. Wexler says that an accurate and detailed family history is the most important information for a doctor to have about a patient--and a patient does not need to know anything about their own genetic code to provide that. 

"Find out what your parents have, what runs in your own family," Wexler says. "That is number one super-crucial....You're giving the doctor crucial information about how to take care of you."

As research and understanding of human genetic makeup has advanced, new legal and ethical issues have arisen. The Genetic Information Nondiscrimination Act of 2007 (GINA) has been passed by the U.S. House of Representatives, and the U.S. Senate was preparing to vote on it at press time. This legislation seeks to protect individuals from discrimination by health care providers, employers and others based on what information their genetic code contains.  

"We want the public to use genetic services, tests and technologies without fear of misuse of their information," says Sharon F. Terry, president and CEO of the Genetic Alliance, via an email interview. "It is simple --one's genetic makeup should be as protected as one's race or gender. This bill creates that protection."

Terry joined Representatives Louise Slaughter (D-NY) and Judy Biggert (R-IL) in introducing the bill before Congress. 

"This bill is the culmination of a bipartisan effort to prohibit the improper use of genetic information in workforce and insurance decisions," said Rep. Slaughter in introducing the bill. "In the 12 years since I first introduced genetic nondiscrimination legislation, the need for it has grown exponentially. Scientific research has advanced so quickly that we cannot afford to wait any longer. This bill will allow us to preserve America's health and protect our scientific edge, all while defending the privacy of our citizens."

"We will never unlock the great promise of the Human Genome Project if Americans are too paranoid to get genetic testing," Rep. Biggert said in the announcement of the legislation in January. "Without the protections offered by [GINA], these fears will persist, research at NIH will slow, and Americans will never realize the benefits of gene-based medicines."

Some new companies are cropping up that offer to sequence their clients' genetic material. For example, a company called 23andMe claims on its Web site to be "developing new ways to help you make sense of your own genetic information." 23andMe declined requests for an interview for this story.

Wexler advises the public to be wary of these types of companies. "This is dangerous," she says. "You need to have genetic counseling around any information that you get back." 

John Blum, the John J. Waldron Research Professor at Loyola University Chicago School of Law, expresses a similar notion. "Knowledge is good, but there is a dark side to knowledge, too," he says.

Blum breaks these new ethical and legal issues down into two different areas. He says the possibility of facing discrimination as a result of one's genetic makeup is a major concern, but that determining how to maintain privacy of this information is the more pressing matter. He says that instead of just dealing with a manifesting disease, people are being forced to face the knowledge that they will possibly or probably develop a particular disease at a later date. This can be especially sensitive and difficult when the disease has no available treatment or cure.   

"Everyone's DNA is different, and everyone's reaction is different--and acceptable," Wexler says. She works with patients who must decide whether or not they will have a test that will tell them if they have the gene for Huntington's disease, and she stresses that this type of information must be handled with the utmost sensitivity and care.

Knowledge of the genome comes not only with the responsibility to protect privacy and to be aware of the possible repercussions of knowing what's contained in one's own genetic code, but it also makes doctors responsible for preventative treatments on a level previously unknown. 

"What if we know so much that we begin providing services way before we need to do that," Blum says. "It's really going to be challenging to factor out what is reasonable and when it is going to be reasonable.... Everything becomes like a statin drug. It raises profound issues about scope of coverage. This is a current problem anyway, but this will push the envelope."

Access to the medical benefits of this understanding of the human genome could also further widen the gap between the health care available to high- and low-income people. 

"I find out I have a genetic marker for something--I have money and insurance and can do something about it," Blum says. 

Blum adds that people without coverage and funds can do little to prevent or treat disease, even when they know it will affect them. Furthermore, getting the genetic screen in the first place might be difficult for people without health care, so prevention might not even be possible. Blum explains a possible scenario. 

"If I am a baby boomer with power and money, I might be able to pressure the pharmaceutical company to help me [with an illness]," Blum says. "This will exacerbate the inequity. It could really benefit a small segment of the population."

Wexler says that people should be active participants in their medical care and be aware of their own health risks by having a good understanding of their family health history. She recommends people approach their health care in the same way they do other services for which they pay. 

"The most crucial thing is to be an educated consumer," says Wexler. 

Published: August 07, 2007
Issue: Fall 2007