Table of Contents | Chapter 4
Howard's Health Is Up to Him
(or is it?)
Howard will turn 50 soon, and it worries him. His grandfather died of a heart attack in his fifties, and so did his father and uncle.
Several years ago, a doctor told Howard that he was at high risk for heart disease because of his family history. But the doctor said that Howard could improve his chances if he lost some weight, stopped smoking, and exercised. The doctor also told Howard to come back every year for a checkup.
Howard hasn't gone on a diet, and he hasn't given up his cigarettes or taken up exercise. He also hasn't been back to the doctor. He's afraid of what the doctor might find.
Howard can't make up his mind. Sometimes he thinks he should try to take better care of his health. Other times, he thinks that he should just accept the fact that he won't live much longer and should get as much fun out of life while he can.
If you were Howard, what would you do?
Researchers now believe that some of the roots of cancer, high blood pressure, and perhaps even alcoholism are found in the genes. They also believe that genes may play a role in the development of certain cases of obesity, some types of depression, and diabetes. The more they search, the more they are finding a link between genes and disease.
However, the truth is always complicated. It isn't so simple as "if you have the gene for a disease, you will get the disease." Here are some of the reasons why:
The truth is that everyone has at least a handful of "problem" genes. Your genes may never cause you trouble...
- While genes play a role in many disorders, so do the conditions and circumstances of your life and the decisions you make. In other words, heredity may influence your health, but so does your environment. For example, some people have genes that put them at risk for cancer. However, their chance of actually getting cancer may be much less if they do not smoke. Some people have genes that put them at risk for diabetes. But, they may never become diabetic if they watch their weight.
Some people have genes that put them at risk for asthma. Still, they may only begin to wheeze and cough when cats are nearby. Diet, exercise, levels of stress, and access to health care are just a few of the many environmental factors that can influence the course of a gene-related disorder. Some factors in your environment are under your control, and some are not. Either way, they can affect the progress of gene-related disorders.
- Only a few human diseases are triggered by a single gene working by itself. In most cases, a disease results from the actions of many genes. An example of a single-gene disorder is Huntington's disease, which was discussed in the last chapter. One error in one gene leads to the fatal health problems of HD. Multiple-gene disorders, where several mutated genes come into play to trigger the problem, are much more common. Examples of multiple-gene disorders include breast cancer, asthma, and diabetes.
- The "strength" of the genes involved in a disorder can affect its progress. Scientists call this genetic expression. Take two people who have the same disease-causing gene and have pretty much the same lifestyle. In one of those persons, the gene "expresses itself" mildly. The failures in its instruction for producing a protein are rather minor. Enough of the protein is produced so that the body can stay healthy for a long time. The disease moves slowly if and when it appears. In the other person, the gene "expresses itself" strongly. The failures in its instruction for making a protein are major. A necessary protein does not get produced or is produced in the wrong amounts. The body cannot stay healthy. That person becomes ill at an early age or comes down with a severe case of the illness.
- In many cases, different mutations in different genes can lead to the same basic problem. An example of this is the albino condition that affected Martin, discussed in Chapter 1. The lack of skin, eye, and hair color can be caused by mutations in several different genes that are involved in the making of pigment. In some cases, the mutations result in patches of colorless skin or hair. With other mutations, the entire body has no pigment. Often, a person who has genes that cause albino coloring also has mutations in other genes that lead to mental retardation and growth problems. In each case, the disorder is called "albinism." However, the genes involved are different, and the result is slightly different, too.
- While there are many diseases that involve mutated genes, the reverse is not true. Many mutated genes do not lead to disease. Sometimes people have what look like "problem" genes because they are different from those of many other people. However, these unusual gene variations don't necessarily lead to disease.
- Some people carry a gene mutation that causes a disorder, but are not at risk for the disorder themselves. This happens when the gene mutation is recessive. You need to inherit two such mutated genes (one from each parent) for the disease to be triggered. If you inherit only one, you won't get sick. You will, however, be a carrier to the next generation. This means that you may pass on the mutated gene to your children without ever showing any symptoms yourself. Your children will be at risk for getting the disease only if they inherit the disease-causing gene mutation from both you and their other parent. An example of a recessive disorder is sickle cell anemia, which was discussed in the last chapter.
- Some disorders occur when healthy genes become damaged. Gene damage can be caused by exposure to radiation or by a viral infection. It also can happen if you come into contact with cancer-causing substances, called carcinogens. Aging also introduces errors into the DNA. Depending on which genes have been damaged, and how many, different disorders may be triggered. Some people's genes appear to be more easily damaged than others. Such people are at higher risk for disorders caused by damage to healthy genes.
- ...if factors in your environment do not "trigger" the genes for a disorder...
- ...if you only have some, but not all, of the genes that come into play to cause a particular disease...
- ...if your genes for disorders don't express themselves strongly...
- ...if you have genes that only lead to a mild form of a disease or disorder...
- ...if your unusual genes have no effect on health...
- ...if your genes for disorders are recessive and you inherit only one copy, and...
- ...if your genes are not damaged by substances in the environment or by aging.
Research tells us that there is no simple link between genes and disorders. Genes have something, but not everything, to do with disorders. Genes do not equal fate.
However, it is easy to fall into that simple way of thinking. The misunderstanding that genes by themselves can determine what happens to you is called genetic determinism. Genetic determinism can lead people to make harmful and unfair judgments about themselves and others.
This kind of simple thinking is leading Howard to fear that, no matter what he does, he will die of a heart attack just like his father, uncle and grandfather. The fact that three of Howard's close relatives died of heart attacks strongly suggests that Howard himself is at risk. He may have inherited genes that make his body less able to resist heart disease.
Researchers don't yet know how many genes are involved in heart disease or how they work to bring about the illness. There is no test yet that can tell Howard whether he has any or all of the genes that can lead to a heart attack.
However, researchers do know something about the kinds of behavior that can trigger heart disease. They know that it occurs more often in people who smoke, have high blood pressure, eat high-fat diets, and do not exercise.
So maybe the reason that Howard's relatives died of heart attacks is that they smoked, worried a lot, ate fatty foods all the time, and sat around too much. Maybe Howard can improve his chances by taking better care of himself.
On the other hand, it is possible that Howard's family carries heart disease genes that express themselves very strongly. It is possible that no matter what Howard does to keep fit, he can't stop those genes from bringing on a heart attack.
The fact remains that Howard simply does not know what his risks are. The way that genes and other factors work together to produce heart disease is so complicated that doctors may never be able to make any safe predictions.
Of course, Howard also needs to remember that his cause of death could have nothing to do with genes. A car accident or a bolt of lightning could get him tomorrow. No matter how much Howard learns about his genes, he will never be able to read his future.
Dealing with Genetic Knowledge
Like Howard, we all must make decisions about the way we live our lives. More and more, however, our decisions will be influenced by information we have about our genes.
Not too far in the future could be a single test that will examine thousands of your genes. The test will reveal whether any of these genes are unusual or defective.
Knowing your genetic profile could be very helpful to you. It could suggest what health-related behaviors you should follow. It could tip you off to have frequent checkups for genetic conditions for which you are at risk. It could help you plan your life so that you avoid behaviors and substances that trigger diseases.
At the same time, knowing your genetic profile could create problems for you. As we said earlier, everyone has a number of "problem" genes. For the most part, you don't know what your problem genes are, and you never will find out unless a health problem surfaces. A piece of paper that lists these "problem" genes could give you a lot of things to worry about that may never come to pass.
It is possible that people who learn their genetic profile will limit the choices they make based on such fears. People may choose not to marry or build a career because they believe that they are doomed by their "problem" genes. The expectation of disease may ruin their enjoyment of life.
A big question is whether children should be told information about the genes they carry or, if so, at what age they should be told. It can be difficult for children to understand some of the important facts about genetics, such as the difference between a risk and a sure thing. There is the possibility that they will misunderstand what they are told.
There also is the risk that they will not be mature enough to cope with the information. For example, if a girl has the gene that puts her at high risk for breast cancer when she is in her forties, should she be told? It may seem that the best thing is to avoid getting this information. However, many parents want to know if their children are at risk for genetic disorders. That way, the parents can be prepared and get treatment for the children in time. They also could make lifestyle choices to avoid triggering the disorder in their child. Parents will have to decide whether and how to share genetic information with their children. Society also may have some say in how genetic information is shared with children, through standards, laws, and regulations that are developed.
|New gene therapies will be expensive. Who will be able to afford them?|
Discrimination Based on Genes
For some people, information about their "problem" genes can bring extra trouble. For example, it can cost them their health insurance. People with "problem" genes have been refused health insurance or dropped from their health plans. In other cases, they have been told that medical expenses for their genetic condition will not be covered. In still others, they have been told that their children will not be covered because they are at risk for inheriting genetic diseases. The number of such cases may increase as genetic testing becomes more common.
You might think that it makes sense to keep genetic information about you to yourself. But this may not be possible. Part of your genetic profile may be obvious to others from your family's medical history. Also, the results of genetic tests usually go into your medical records. Insurance companies may demand to see these records before they will cover you.
Some people are concerned that employers may try to use genetic information to weed out workers who are sick, or who may someday become sick, because of a genetic disorder. Under the 1990 Americans with Disabilities Act (ADA), it is against the law to discriminate against workers who are disabled. The federal Equal Employment Opportunity Commission has ruled that the ADA also protects people from discrimination based on their genetic profile.
However, the fear of being discriminated against may lead people to refuse genetic testing even when it could help diagnose, prevent or treat a health problem. They may be too afraid that the information will be used against them. If that happens, then all the benefits of genetic research could come to nothing.
Genes and Behavior
In Howard's case, it didn't take any special genetic test to reveal that he is at risk for a heart attack. His risk is clear from his family's medical history and from his own smoking, eating, and exercise habits. Given these facts, Howard has a choice: whether or not to reduce his risk by adopting a healthier lifestyle.
But this raises an interesting question: How much control does Howard have over the choices he makes? If Howard decides to change his ways, is that because his genes have made him a careful person? If Howard rejects his doctor's advice, is that because his genes have made him reckless?
The study of whether and how traits for behavior are inherited is called behavioral genetics. Scientists have long tried to figure out whether behavior is shaped by our genes or by how we are raised. It is called the question of "nature versus nurture." For a long time, scientists took one position or the other. They believed that either nature or nurture was responsible, but not both. Today, most scientists agree that both genes (nature) and environment (nurture) help make us who we are. What no one knows is just how nature and nurture work together.
Some researchers believe that genes shape our inborn frame of mind, or temperament. According to this theory, we may inherit our tendency to be shy or bold, risk-taking or cautious. However, any temperament we inherit is shaped and altered by our experiences from the moment we are born..For example, a shy boy who is encouraged to try out new situations may learn to be more outgoing. Another shy child who is pushed too quickly into strange situations may always remain timid. So might a shy child who is allowed to hide behind his parents.
There is some evidence that to some degree, abilities also may be inherited. But any such genetic trait is heavily shaped by experience. A girl who is never allowed to play sports may never develop her inborn athletic talent. The reverse also is true. A girl whose genes do not give her any athletic advantage may still become a star if she is encouraged to play, practices hard, and keeps at it.
Many people are interested in how genes shape other personal characteristics, such as sexual orientation, intelligence, and social behavior. Research into these areas is very controversial and raises many questions. For example, some researchers are trying to find out if there are any genes that contribute to homosexuality. But what if there are, and what if there aren't? If homosexual identity is caused in part by the genes, does this mean that society should be more accepting of it? On the other hand, should society be more accepting of homosexual behavior even if it is purely a lifestyle choice?
Other researchers are trying to determine how genes shape intelligence. The question is, what do we do with this information? If intelligence is controlled in part by the genes, should society spend more money educating those who lack genetic smarts to give them a boost? Or should it spend more money on the genetically gifted, who could make more use of the education? And take the question of a genetic link to criminal behavior. If such a link is found, should the police keep close tabs on people with "criminal" genes? Should such people be excused for crimes they commit, since their genes are at fault?
Some people are critical of theories linking genes and certain kinds of behavior. They say that these theories are often based on fanciful thinking or prejudice, not science. They say that this kind of research is easily twisted to support discrimination against minorities. In any event, research suggests that environment is at least as powerful a shaper of behavior as genes. And there is still the role of personal responsibility. Shy or bold, risk-taking or cautious, it is still within Howard's power to choose whether to quit smoking, to give up sweets, and to start jogging. Most researchers do not believe that our genes fully explain our behavior.
As you can see, genetic research doesn't give us all the answers. But it surely does open up some interesting questions. This is particularly true for the part of health care that has to do with making babies. That's the subject of our next chapter.
Your Genes, Your Choices is a publication of Science + Literacy for Health, a project of the AAAS Directorate for Education and Human Resources. The publication was funded by the U.S. Department of Energy. The website was built by Mike Wooldridge. Send feedback to SciLit@aaas.org.