The Human Genome Project and the Future of Medicine

by Todd Gary, Ph.D.

It has been said, “Knowledge is power.” Nowhere is this more evident than in the field of medicine. Knowledge plays a crucial role in the proper diagnosis and care of patients. At some point in the next 20 years, patients will be screened for thousands of genetic mutations and diseases with a routine lab test. The knowledge gleaned from this genetic profile will allow an exact diagnosis and assist in choosing the proper treatment. Also, this test will indicate whether the person has a genetic predisposition for certain diseases or conditions such as diabetes, heart disease, or Alzheimer’s. This exciting diagnostic tool is currently being developed in this country, and will be extremely exciting for nurses involved in patient care.

For the first time in history, the genetic makeup of a human is known. This was a result of the Human Genome Project, one of the largest scientific projects in history. When this result was announced by President Clinton on June 26, 2000, he stated, “We are learning the language in which God created life…without a doubt, this is the most important, most wondrous map ever produced by humankind.” The results of the Human Genome Project have been described as the greatest scientific discovery of the 20th century. Leading scientists predict these results will change the field of medicine forever and insist that the 21st century will focus on applying this information in exciting ways such as the lab test described above.

While these claims have been made and this research has been mentioned frequently in the media, most health care professionals are not familiar with this project, its results, and how it will impact the health care industry. This article is meant to familiarize the Tennessee nursing community with the Human Genome Project and the areas in which it will impact nursing and patient education.

A genome is all of the genetic material found in the chromosomes of an organism. This material has a major role in determining the health of the organism, and is passed on to the organism’s offspring. The human genome consists of 23 pairs of chromosomes. Males have 22 pairs of chromosomes and the 23rd pair consists of an X and a Y chromosome. Females have 22 pairs of chromosomes and the 23rd pair consists of two X chromosomes. These chromosomes are composed of DNA (deoxyribonucleic acid).

The structure of each molecule of DNA is like a ladder built with sugar and phosphate. The rungs of the ladder are formed by four different substances (adenine, cytosine, guanine, and thymine) called bases which are denoted by the letters A, C, G, and T. Millions of these rungs or bases connect to form a very large molecule called a chromosome. In humans, one copy of our 23 chromosomes contains 3.1 billion bases of DNA. If the sequence of these bases were written in letter code like AACTGAAGC, the 3.1 billion letters (at 300 letters per line) would fill 300 New York City phonebooks.

The DNA sequence of Homo sapiens was published in February 2001 and is available online. This is the result of work by a consortium of 20 countries, which include Australia, Brazil, Canada, China, Denmark, France, Germany, Israel, Italy, Japan, Korea, Mexico, the Netherlands, Russia, Sweden, the United Kingdom, and the United States. To determine the sequence of 3.1 billion bases of DNA found in all humans, 1,000 bases of DNA were sequenced (or identified) per second 24 hours a day (every day) for 10 years.

Dr. Francis Collins directed this international Human Genome Project. Dr. Collins has both an MD and a PhD, and was one of the co-discoverers of the cystic fibrosis gene. As a physician, he is interested in medical applications of the human genome. Independently, the for-profit company Celera sequenced the human genome as well. The results of the international effort and that of Celera were summarized in the February 2001 issues of two of the best scientific journals in the world: Science and Nature. The complete sequence is available online.

Within the sequence of DNA bases that make up chromosomes are genes. Genes are specific DNA bases that direct the timing and synthesis of proteins. These proteins function to keep us alive and healthy. Humans have about 35,000 genes. The traits we inherit from our ancestors depend on the DNA sequence in these genes. If a mistake in the DNA sequence is present in a gene, the ensuing protein may function less or not at all. This contributes to genetic diseases such as cystic fibrosis, sickle cell anemia, and 4,000 known genetic disorders. These mistakes in the DNA are then passed on to the offspring.

The sequence of DNA is much like the sequence of 0 and 1 in a computer program. Everything in a computer program can be defined in terms of 0 and 1. Computer storage is based on bits: kilobits (kb), megabits (mb), and gigabits (gb). These bits are the sequence of 0 and 1 that define a character, such as a letter in the alphabet. The letter A in computer language is 00100101, and the letter B is 00100111. The zeros and ones can also direct the computer. For example, the instruction 00101111 directs the computer to divide two numbers. The instruction 00101010 directs the computer to multiply the numbers. If the wrong 0 or 1 is programmed into the computer, the wrong character will be assigned and an error will be introduced into the program.

Genes run the human computer program. Humans have about 35,000 genes in our genome of which we know the function for 15,000. These genes all contain the instructions to make all of the proteins to allow us to think, walk, talk, sleep, eat, and more. If a base (A, C, T, or G) is located in the DNA where it should not be, this can introduce an error into the genetic program of the organism. For example, missing three letters out of three billion can make a huge difference. If you are missing CTT at a specific site within the genome, you carry cystic fibrosis.

Another similarity between computer codes and DNA is that some errors are more severe than others. We have all noticed an error we call a bug in a computer program. Some of these errors are not very noticeable while others cause our entire computer to freeze up and become unusable until it is rebooted. Humans cannot be rebooted, but we can read the human code, know where an error is located, and predict how this will affect the health of an individual.

The severity of the error is dependent upon the location. If the error is located outside of a gene, it will go unnoticed. If the error is located within a gene, the protein programmed to be produced can have a lowered function or no function. This can lead to greater or less severity in the disorder. Now the task is to find out what all of these proteins do, as differences in DNA within these genes alter the health of individuals.

The sequencing of the human genome already is having an impact on finding genes associated with disease. Over 30 genes have been pinpointed and associated with breast cancer, muscle disease, deafness, and blindness. Additionally, this research is aiding in finding the DNA sequences that underlie such common diseases as cardiovascular illness, diabetes, arthritis, and cancer. Knowing which genes are involved will help in the development of effective new therapies.

Scientists are beginning to develop a chemical process for building a device that could help doctors predict a patient’s response to drugs or screen patients for thousands of genetic mutations and diseases, all with one simple lab test. This test involves a DNA chip similar to a computer chip, but imbedded with DNA molecules instead of electronic circuitry. It is designed to probe a biological sample for genetic information that indicates whether the person has a genetic predisposition for certain diseases or conditions. The chip would have thousands of unique sequences of DNA embedded. If a patient’s DNA matches any of these sequences, it will bind to it like two pieces of Velcro. A machine would be used to detect this binding.

The chip can screen for the genes linked to breast cancer, cystic fibrosis, or prostate cancer. For example, women who carry a specific genetic mutation known as BRCA-1 have a genetic form of breast cancer. They are seven times more likely to get breast cancer than women who have the normal DNA sequence in this region, as well as a more malignant form of breast cancer earlier in life. The specific DNA sequence that includes the BRCA-1 mutation would be embedded into the DNA chip. Only DNA from the affected women would match and bind to the embedded BRCA-1 DNA sequence.

This binding would be detected during the lab test, and the patient’s health care professional would know to closely monitor the patient as well as educate the patient on her genetic risks. In the year 2010, these DNA chips could be used to routinely screen for the 10 most common genetic conditions. In fact, one company, Affymetrix, predicts that in five years they will have developed a DNA chip that will test for over 100,000 genetic conditions.

These DNA chips allow a precise diagnosis, which will ensure the most effective treatment. For example, a genetic fingerprint will allow doctors treating prostate cancer to predict how aggressive a tumor will be. This information will help weigh the risks and benefits of different treatments. By analyzing the patient’s DNA, this molecular diagnosis can be used to determine the exact cause. Additionally, the severity of the disorder can be determined. Once DNA sequence changes in a gene are correlated to severity, people can be tested for risks of developing conditions such as diabetes. This will alert patients and health care professionals to the risk before it becomes a problem. Also, a genetic code may determine how well a person will respond to a certain drug. Some people have better responses than others to hypertension drugs or chemotherapy, for example.

Dr. Collins, director of the Human Genome Project, created the following case study to illustrate how he thinks results from the Human Genome Project will be used in diagnostic medicine in the year 2015:

John is a 21-year-old patient whose dad has just died at 45 of a heart attack. John is a pack-a-day smoker, has a cholesterol level of 255, and is very concerned about his own health. He is at a very teachable moment in his life. He is inquiring about his own health. His physician recommends genetic tests from a blood sample and asks John for permission to test other genetic markers. John agrees. He is given an educational CD-ROM and access to nurses who are educated in genetics. Two weeks later, the results are in, and John meets with his physician. He is told the good news. He has genetic markers that place him at a lower lifetime risk of the following disorders: prostate cancer (7% lifetime risk) and Alzheimer’s disease (8%). He is also told the bad news. John is at a greater risk of coronary artery disease (70% lifetime risk), lung cancer (40%), and colon cancer (23%). He can substantially lower the risk through changes in diet, pharmaceutical intervention, and support. With proper intervention over time, his lifetime risks drop to the following: coronary artery disease (70% to 15%), lung cancer after he stops smoking for five years (40% to 6%), and colon cancer (23% to 8%). This information will be empowering for John. Since most forms of cancer require several stages, John’s health can be monitored more closely over time by following up with diet, intervention, and his support group.

Today, the three leading causes of death are heart disease, cancer, and stroke. If…how…and when…one gets these diseases depend in part on genes and in part on one’s lifestyle. Dr. Collins’ example illustrates how knowledge of the genetic makeup can assist patients in positively altering their lifestyle.

One of the most important discoveries of the 20th century was identifying and reading the code of life, the Human Genome Project. This discovery will give health care professionals greater knowledge about their patients. They will have the ability to identify the genetic predisposition of their patients and more precisely diagnose and treat current and future problems. In this new century, nurses will become even more valuable in patient education. They will be better equipped to give patients and their families more accurate information about their personal health and guide them in maximizing their quality of life.

Dr. Todd Gary is an award winning scientist and science educator. Currently, he is an Associate Professor of Biology and a Research Specialist in the Center of Excellence in Information Systems at Tennessee State University. His research interests include the genetic basis of cancer and how space travel affects gene expression in plants and animals. This article is based on Dr. Gary’s presentation “The Human Genome Project and the Future of Medicine” at the Tennessee Nurse Association’s Annual Convention in 2000. He can be reached by email

Publications cited.

Lander, E. S. et al. Initial sequencing and analysis of the human genome. Nature 409, 860-921 (February 15, 2001).
Venter, J.C. et al. The sequence of the human genome. Science 291, 1304-1351 (February 16th, 2001).