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  3. A controversy erupted in the scientific community in early 1998 over the use of DNA (deoxyribonucleic acid) fingerprinting in cr

A controversy erupted in the scientific community in early 1998 over the use of DNA (deoxyribonucleic acid) fingerprinting in cr

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问题      A controversy erupted in the scientific community in early 1998 over the use of DNA (deoxyribonucleic acid) fingerprinting in criminal investigations. DNA fingerprinting was introduced in 1987 as a method to identify individuals based on a pattern seen in their DNA, the molecule of which genes are made. DNA is present in every cell of the body except red blood cells. DNA fingerprinting has been used successfully in various ways, such as to determine paternity (父亲的身份) where it is not clear who the father of a particular child is. However, it is in the area of criminal investigations that DNA fingerprinting has potentially powerful and controversial uses.
     DNA fingerprinting and other DNA analysis techniques have revolutionized criminal investigations by giving investigators powerful new tools in the attempt to prove guilt, not just establish innocence. When used in criminal investigations, a DNA fingerprint pattern from a suspect is compared with a DNA fingerprint pattern obtained from such material as hairs or blood found at the scene of a crime. A match between the two DNA samples can be used as evidence to convict a suspect.
     The controversy in 1998 stemmed from a report published in December 1991 by population geneticists Richard C. Lewontin of Harvard University in Cambridge, Mass, and Daniel L. Hartl of Washington University School of Medicine in St. Louis, Mo. Lewontin and Hartl called into question the methods to calculate how likely it is that a match between two DNA fingerprints might occur by chance alone. In particular, they argued that the current method Cannot properly determine the likelihood that two DNA samples will match because they came from the same individual rather than simply from two different individuals who are members of the same ethnic group. Lewontin and Hartl called for better surveys of DNA patterns.
     In response to their criticisms, population geneticists Ranajit Chakraborty of the University of Texas in Dallas and Kenneth K. Kidd of Yale University in New Haven, Conn. , argued that enough data are already available to show that the methods currently being used are adequate. In January 1998, however, the Federal Bureau of investigation and laboratories that conduct DNA tests announced that they would collect additional DNA samples from various ethnic groups in an attempt to resolve some of these questions. And, in April, the National Academy of Sciences called for strict standards and system of accreditation (鉴定合格) for DNA testing laboratories.  
According to the passage, DNA fingerprinting can be unreliable when ______ .
选项 A、the methods used of blood cell calculation are not accurate
B、two different individuals of the same ethnic group may have the same DNA fingerprinting pattern
C、a match is by chance left with fingerprints that happen to belong to two different individuals
D、two different individuals leave two DNA samples
答案B
解析 第三段倒数第二句提到，基因学家争论说目前的方法还不能确定两个相匹配的DNA样品是来自同一个人，或者仅仅是来自同一个民族的不同的人，这是本篇文章争论的要点。由此推断出，当两个来自同一民族的不同的人有着相同的DNA指纹模式时，DNA指纹鉴定就不可靠了，故答案为B项。
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