Does Measurement Measure Up?: How Numbers Reveal and Conceal the Truth

CHAPTER 7: MAN: The Measure of All Things

CHAPTER 7 MAN The Measure of All Things To define genes by the diseases they cause is about as absurd as defining organs of the body by the diseases they get. . . . It is a measure, not of our knowledge, but of our ignorance. —Matt Ridley, Genome: The Autobiography of a Species in 23 Chapters When Richard Buckland confessed to the rape and murder of 15-year-old Dawn Ashford, the police in Leicestershire, England, thought the case was closed. In addition to his confession, Buckland knew details about this 1986 crime that had not been released to the public. But Buckland refused to confess to the rape and murder of another 15-year-old girl, and the police were convinced the same man had committed both crimes. Semen samples from both victims revealed the blood type of the murderer was the same in both cases, and other aspects of the crimes strongly suggested a single assailant. Dr. Alec Jeffreys and his colleagues at Leicester University had recently developed a technique for creating what are now known as DNA profiles, and the Leicestershire police contacted him, almost as a last resort. Jeffreys first compared Buckland’s DNA to that of the semen samples. He proved the police were right, one man had committed both crimes, but at the same time wrong, since that man was not Richard Buckland. Independent confirmation of Jeffreys’s tests made Richard Buckland the first person ever to be exonerated by DNA profiling. Good news for Buck- D OES M EASUREMENT M EASURE U P ? 116 land, but the police still had two unsolved murders on their hands. They decided to carry out the world’s first mass DNA screening. All the adult men in three neighboring villages, about 5,000 in all, were asked to volunteer to provide blood or saliva samples. About 10% of the men matched the blood type of the murderer, and they were all then given full DNA profiles. This took six months—but there were no matches. Then, one year later, a woman came forward to say she had overheard her colleague, Ian Kelly, bragging that he had given his DNA sample under false pretenses. In fact, Kelly had masqueraded as his friend, Colin Pitchfork. Based on this evidence , Pitchfork was arrested and his DNA matched the semen in both victims. Pitchfork was sentenced to life in prison in 1988. Jeffreys coined the term ‘‘genetic fingerprinting,’’ and his technique literally answers the question ‘‘Who are we?’’ Since the human genome inside each of us (and in each of our body’s cells) is unique, genetic fingerprinting can be used to identify each of us with absolute certainty (unless you happen to have an identical twin). We speak of ‘‘the’’ human genome, and this is nearly correct—only about 0.1% of our genetic material varies from one person to the next. But that 0.1% still leaves about 3 million base pairs of DNA that differ—more than enough to allow us to identify one another. Only about 5% of the human genome is made up of genes. The other 95% is known as noncoding DNA (or sometimes as ‘‘junk’’ DNA). Although noncoding DNA does not include genes, it does have important functions that are becoming better understood all the time. The use of noncoding DNA in genetic fingerprinting is a complex combination of molecular biology, biochemistry, and statistics. The technique was first used as evidence in court in 1985. The Pitchfork murder trial was the first time DNA evidence was ever used to both exonerate the prime suspect and convict the real murderer. Since then, the techniques have been greatly improved and streamlined, so that DNA fingerprinting has become more versatile, cheaper, faster, and more reliable. In some ways, the development and use of DNA fingerprinting mirrors the development of old-fashioned fingerprinting (the kind done on fingers ). Among the first uses of traditional fingerprints was simply identifying people—confirming that they were who they said they were (for example, in India, the ruling British used fingerprints to identify Indians who could not sign their own names). The first use of DNA fingerprints was similar. After M AN : T HE M EASURE OF A LL T HINGS 117 the basic science had been developed in England, the technique was used to verify the claims of would-be immigrants that they were the close...