of Contents | Chapter
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.
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.
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
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?
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:
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 truth is that everyone has at least a handful of "problem" genes. Your
genes may never cause you trouble...
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 can lead to other 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
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
...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
...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
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
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?
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
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,
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
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
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.