Genetics - Real-life applications





T HE G ENETICS R EVOLUTION

In the modern world genetics plays a part in more dramatic breakthroughs than any other

A SCIENTIST STUDIES THE ARRANGEMENT OF CHROMOSOME PAIRS, THE THREADLIKE DNA-CONTAINING BODIES IN CELLS THAT CARRY GENETIC INFORMATION. THE HUMAN GENOME PROJECT IS WORKING TO COMPLETE A MAP OUT-LINING THE LOCATION AND FUNCTION OF THE GENES IN HUMAN CELLS. (© BSIP/V & L/Photo Researchers. Reproduced by permission.)
A SCIENTIST STUDIES THE ARRANGEMENT OF CHROMOSOME PAIRS , THE THREADLIKE DNA- CONTAINING BODIES IN CELLS THAT CARRY GENETIC INFORMATION . T HE H UMAN G ENOME P ROJECT IS WORKING TO COMPLETE A MAP OUT - LINING THE LOCATION AND FUNCTION OF THE GENES IN HUMAN CELLS . (
© BSIP/V & L/Photo Researchers
. Reproduced by permission. )
field of biological study. These breakthroughs have an impact in a wide variety of areas, from curing diseases to growing better vegetables to catching criminals. The field of genetics is in the midst of a revolution, and at the center of this exciting (and, to some minds, terrifying) phenomenon is the realm of genetic engineering: the alteration of genetic material by direct intervention in genetic processes. In agriculture, for instance, genes are transplanted from one organism to another to produce what are known as transgenic animals or plants. This approach has been used to reduce the amount of fat in cattle raised for meat or to increase proteins in the milk produced by dairy cattle. Fruits and vegetables also have been genetically engineered so that they do not bruise easily or have a longer shelf life.

Not all of the work in genetics is genetic engineering per se; in the realm of law, for instance, the most important application of genetics is genetic fingerprinting. A genetic fingerprint is a sample of a person's DNA that is detailed enough to distinguish it from the DNA of all others. The genetic fingerprint can be used to identify whether a man is the father of a particular child (i.e., to determine paternity), and it can be applied in the solving of crimes. If biological samples can be obtained from a crime scene—for example, skin under the fingernails of a murder victim, presumably the result of fighting against the assailant in the last few moments of life—it is possible to determine with a high degree of accuracy whether that sample came from a particular suspect. The use of DNA in forensic science is discussed near the conclusion of this essay.

THE REVOLUTION IN MEDICINE.

Some of the biggest strides in genetic engineering and related fields are taking place, not surprisingly, in the realm of medicine. Genetic engineering in the area of health is aimed at understanding the causes of disease and developing treatments for them: for example, recombinant DNA (a DNA sequence from one species that is combined with the DNA of another species) is being used to develop antibiotics, hormones, and other disease-preventing agents. Vaccines also have been genetically re-engineered to trigger an immune response that will protect against specific diseases. One approach is to remove genetic material from a diseased organism, thus making the material weaker and initiating an immune response without causing the disease. (See Immunity and Immunology for more about how vaccines work.)

Gene therapy is another outgrowth of genetics. The idea behind gene therapy is to introduce specific genes into the body either to correct a genetic defect or to enhance the body's capabilities to fight off disease and repair itself. Since many inherited or genetic diseases are caused by the lack of an enzyme or protein, scientists hope one day to treat the unborn child by inserting genes to provide the missing enzyme. (For more about inherited disorders, see the essays Disease, Noninfectious Diseases, and Mutation.)

THE HUMAN GENOME PROJECT.

One of the most exciting developments in genetics is the initiation of the Human Genome Project, designed to provide a complete genetic map outlining the location and function of the 40,000 or so genes that are found in human cells. (A genome is all of the genetic material in the chromosomes of a particular organism.) With the completion of this map, genetic researchers will have easy access to specific genes, to study how the human body works and to develop therapies for diseases. Gene maps for other species of animals also are being developed.

The project had its origins in the 1990s, with the efforts of the United States Department of Energy (DOE) and the National Institutes of Health (NIH). The NIH connection is probably clear enough, but the DOE's involvement at first might seem strange. What, exactly, does genetics have to do with electricity, petroleum, and other concerns of the DOE? The answer is that the DOE grew out of agencies, among them the Atomic Energy Commission (AEC), established soon after the explosion of the two atomic bombs over Japan in 1945. Even at that early date, educated nonscientists understood that the radioactive fallout produced from nuclear weaponry can act as a mutagen; therefore, Congress instructed the AEC to undertake a broad study of genetics and mutation and the possible consequences of exposure to radiation and the chemical by-products of energy production.

Eventually, scientists in the AEC and, later, the DOE recognized that the best way to undertake such a study was to analyze the entire scope of the human genome. The project formally commenced on October 1, 1990, and is scheduled for completion in the middle of the first decade of the twenty-first century. Upon completion, the Human Genome Project will provide a vast store of knowledge and no doubt will lead to the curing of many diseases.

Still, there are many who question the Human Genome Project in particular, and genetic engineering in general, on ethical grounds, fearing that it could give scientists or governments

THE EXPLOSION OF AN ATOMIC BOMB OVER NAGASAKI, JAPAN, DURING WORLD WAR II (SEPTEMBER 1, 1945). THE RADIOACTIVE FALLOUT PRODUCED FROM NUCLEAR WEAPONRY CAN ACT AS A MUTAGEN, ALTERING THE CHEMICAL OR PHYSICAL MAKEUP OF DNA. (© Bettmann/Corbis. Reproduced by permission.)
T HE EXPLOSION OF AN ATOMIC BOMB OVER N AGASAKI , J APAN , DURING W ORLD W AR II (S EPTEMBER 1 , 1945 ). T HE RADIOACTIVE FALLOUT PRODUCED FROM NUCLEAR WEAPONRY CAN ACT AS A MUTAGEN , ALTERING THE CHEMICAL OR PHYSICAL MAKEUP OF DNA. (
© Bettmann/Corbis
. Reproduced by permission. )
too much power, unleash a Nazi-style eugenics (selective breeding) program, or result in horrible errors, such as the creation of deadly new diseases. In fact, it is impossible to search "genetic engineering" on the World Wide Web without coming across the Web sites of literally dozens and dozens of agencies, activist groups, and individuals opposed to genetic engineering and the mapping of the human genome. For more about the Human Genome Project, genetic engineering, and their opponents, see Genetic Engineering.

G ENETICS IN F ORENSIC S CIENCE

Forensic science, as we noted earlier, is the application of science to matters of law. It is based on the idea that a criminal always leaves behind some kind of material evidence that, through careful analysis, can be used to determine the identity of the perpetrator—and to exonerate someone falsely accused. Among those forms of material evidence of interest to forensic scientists working in the field of genetics are blood, semen, hair, saliva, and skin, all of which contain DNA that can be analyzed. In addition, there are areas of forensic science that rely on biological study, though not in the area of genetics: blood typing as well as the analysis of fingerprints or bite marks, both of which have patterns that are as unique to a single individual as DNA is.

One of the first detectives to use science, including biology and medicine, in solving crimes was a fictional character: Sherlock Holmes, whose creator, the British writer Sir Arthur Conan Doyle (1859-1930), happened to be a physician as well. The first full-fledged (and real) police practitioner of forensic science was the French police official Alphonse Bertillon (1853-1914), who developed an identification system that consisted of a photograph and 11 body measurements, including dimensions of the head, arms, legs, feet, hands, and so on, for each individual. Bertillon claimed that the likelihood of two people having the same measurements for all 11 traits was less than one in 250 million. In 1894 fingerprints, which were easier to use and more unique than body measurements, were added to the Bertillon system.

Fingerprints, unlike DNA, are unique to the individual; indeed, identical twins have the same DNA but different fingerprints. Mark Twain (1835-1910) could not have known this in 1894, when he published The Tragedy of Pudd'nhead Wilson, and the Comedy of Those Extraordinary Twins. Nonetheless, the story involves a murder committed by one man and blamed on his twin, who eventually is exonerated on the basis of fingerprint evidence—still a new concept at the time. In some situations, however, fingerprint evidence may be unavailable, and though law-enforcement agencies have developed extraordinary techniques for analyzing nearly invisible (i.e., latent) prints, sometimes this is still not enough.

THE SIMPSON CASE AND THE CONTROVERSY OVER DNA EVIDENCE.

For example, in the infamous murder of Nicole Brown Simpson and Ron Goldman on June 12, 1994, fingerprint evidence would have been ineffective in the case against the suspect, the former football star and actor O. J. Simpson. Since Nicole Simpson was his ex-wife,

O. J. SIMPSON REACTS TO THE JURY'S VERDICT. DESPITE DNA EVIDENCE THAT LINKED BLOOD AT THE CRIME SCENE WITH BLOOD IN HIS CAR, THE JURY FOUND HIM NOT GUILTY OF DOUBLE MURDER. (AP/WIde World Photos. Reproduced by permission.)
O. J. S IMPSON REACTS TO THE JURY ' S VERDICT . D ESPITE DNA EVIDENCE THAT LINKED BLOOD AT THE CRIME SCENE WITH BLOOD IN HIS CAR , THE JURY FOUND HIM NOT GUILTY OF DOUBLE MURDER . (
AP/WIde World Photos
. Reproduced by permission. )
the appearance of his prints at the scene of her murder in her Los Angeles home could be explained away easily, even though she had taken out a restraining order against her former husband (who she had accused of spousal abuse) some time before the murder. Rather than fingerprints, the prosecution in his murder trial used DNA evidence connecting blood at the crime scene with blood found in Simpson's vehicle. (Some of this blood was apparently his own, since he had mysterious cuts on his hands that he could not explain to police officers.)

A jury found Simpson not guilty on October 3, 1995, and jurors later claimed that the prosecution had failed to make a strong case using DNA evidence. Furthermore, they cited police contamination of the DNA evidence, which had been established in their minds by Simpson's defense team, as a cause for reasonable doubt concerning Simpson's guilt. In fact, assuming that the defense was fully justified in this claim, that would have meant only that the DNA samples would have been less (not more) likely to convict Simpson.

At the same time, a number of legitimate concerns regarding the use of DNA evidence were raised by experts for the defense in the Simpson trial. Samples can become contaminated and thus difficult to read; small samples are difficult for analysts to work with effectively; and results are often open to interpretation. Furthermore, the outcome of the Simpson case illustrates the fact that findings based on DNA evidence are not readily understood by non-specialists, and may not make the best basis for a case-particularly in one so fraught with controversy. The prosecution based its case almost entirely on extremely technical material, explained in excruciating detail by experts who had devoted their lives to studying areas that are far beyond the understanding of the average person. Attempting to wow the jurors with science, the prosecution instead seemed to create the impression that DNA evidence was some sort of hocus-pocus invented to frame an innocent man. Simpson went free, though the jury in a 1996 civil trial (which took a much simpler approach, eschewing complicated DNA testimony) found him guilty.

DNA EVIDENCE SUCCESS STORIES.

Because of the Simpson case, the use of DNA evidence gained something of a bad name. Nonetheless, it has been successful in less high profile cases, beginning in 1986, when English police tracked down a rapist and murderer by collecting blood samples from some 2,000 men. One of them, named Colin Pitchfork, paid another man to provide a sample in his place. This attracted the attention of the police, who tested his DNA and found their man.

Since that time, DNA evidence has been used in more than 24,000 cases and has aided in the conviction of about 700 suspects. The DNA in such cases is not always obtained from a human subject. In the investigation of the May 1992 murder of Denise Johnson in Arizona, a homicide detective found two seed pods from a paloverde tree in the bed of a pickup truck owned by the suspect, Mark Bogan. The accused man admitted having known the victim but denied ever having been near the site where her body was found. It so happened that there was a paloverde tree at the site, and testing showed that the DNA in the pods on his truck bed matched that of the tree itself. Bogan became the first suspect ever convicted by a plant.

On the other hand, in some cases, DNA evidence has cleared a suspect falsely accused. Such was the case with Kerry Kotler, convicted in 1981 for rape, robbery, and burglary and sentenced to 25-50 years in jail. In 1988, Kotler began petitioning for DNA analysis, which subsequently showed that his DNA did not match that of the rapist, who had left a semen sample in the victim's underwear. Kotler was released in December 1992 and in March 1996 was awarded $1.5 million in damages for his wrongful imprisonment. The story does not end there, however. Kotler's case turned out to be one of the more bizarre in the annals of forensic DNA testing. Perhaps he did not commit the first rape, but a month after he received the damage award, he was on his way back to prison for the August 1995 rape of another victim. This time prosecutors showed that Kotler's semen matched samples taken from his victim's clothing—and to prove their case, they used DNA testing.

WHERE TO LEARN MORE

Department of Energy Human Genome Program (Web site). <http://www.ornl.gov/hgmis/> .

The DNA Files/National Public Radio (Web site). <http://www.dnafiles.org/> .

Fridell, Ron. DNA Fingerprinting: The Ultimate Identity. New York: Franklin Watts, 2001.

Genetics Education Center, University of Kansas Medical Center (Web site). <http://www.kumc.edu/gec/> .

Henig, Robin Marantz. The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics. Boston: Houghton Mifflin, 2000.

Lerner, K. Lee, and Brenda Wilmoth Lee. World of Genetics. Detroit: Gale Group, 2002.

National Human Genome Research Institute (Web site). <http://www.nhgri.nih.gov> .

Schwartz, Jeffrey H. Sudden Origins: Fossils, Genes, and the Emergence of Species. New York: John Wiley and Sons, 1999.

Tudge, Colin. The Impact of the Gene: From Mendel's Peas to Designer Babies. New York: Hill and Wang, 2001.

Virtual Library on Genetics, Oak Ridge National Laboratory (Web site). <http://www.ornl.gov/TechResources/Human_Genome/genetics.html #x003e; .