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  3. 共用题干 第二篇DNA FingerprintingDNA is the genetic material found within the cell ...

共用题干 第二篇DNA FingerprintingDNA is the genetic material found within the cell ...

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问题 共用题干
第二篇

DNA Fingerprinting

DNA is the genetic material found within the cell nuclei of all living things. In mammals（哺乳动物）
the strands of DNA are grouped into structures called chromosomes（染色体）.With the exception of identical
twins,the complete DNA of each individual is unique.
DNA fingerprinting is sometimes called DNA typing. It is a method of identification that compares bits
of DNA.A DAN fingerprint is constructed by first drawing out a DNA sample from body tissue or fluid such
as hair , blood，or saliva（唾液）.The sample is then segmented using enzymes（酶）,and the segments are
arranged by size.The segments are marked with probes and exposed on X-ray film,where they form a pat-
tern of black bars一the DNA fingerprint.If the DNA fingerprints produced from two different samples match,
the two samples probably came from the same person.
DNA fingerprinting was first developed as an identification technique in 1985.Originally used to detect
the presence of genetic diseases,it soon came to be used in criminal investigations and legal affairs.The first
criminal conviction based on DNA evidence in the United States occurred in 1988.In criminal investiga-
tions,DNA fingerprints derived from evidence collected at the crime scene are compared to the DNA finger-
prints of suspects.Generally,courts have accepted the reliability of DNA testing and admitted DNA test re-
sults into evidence.However,DNA fingerprinting is controversial in a number of areas:the accuracy of the
results,the cost of testing,and the possible misuse of the technique.
The accuracy of DNA fingerprinting has been challenged for several reasons. First,because DNA segments
rather than complete DNA strands are"fingerprinted";a DNA fingerprint may not be unique;large-scale
research to confirm the uniqueness of DNA fingerprinting.test results has not been conducted.In addition,
DNA fingerprinting is often done in private laboratories that may not follow uniform testing standards and
quality controls.Also,since human beings must interpret the test,human error could lead to false results.
DNA fingerprinting is expensive.Suspects who are unable to provide their own DNA to experts may not
be able to successfully defend themselves against charges based on DNA evidence.
Widespread use of DNA testing for identification purposes may lead to the establishment of a DNA
fingerprint database.
选项 DNA fingerprinting is a technique of________.
A:grouping DNA strands into structures
B:segmenting DNA with probes
C:constructing body tissues by enzymes
D:identifying a person by comparing DNAs
答案D
解析本题是事实细节判断题。文章第一段最后一句话“With the exception of identical twins, the complete DNA of each individual is unique."，意思是：除生物姊妹体外（如完全相同的双胞 胎），每一个人的整条DNA是独一无二的。说明双胞胎的DNA是相同的。故选A。
文章第二段对DNA指纹识别进行了解释，可知DNA指纹识别法有时也称DNA印记 法。它是一种通过对比DNA片段来进行辨认识别的方法。故选D。
由文章第三段前两句话可知DNA技术最初是被用来检测基因疾病的，故选D。
文章倒数第三段讲述了人们质疑DNA指纹识别的三个原因：DNA指纹识别针对的是 DNA片段而不是整个DNA系统; DNA指纹识别是在私人实验室进行的很可能没有遵循相同 的鉴定标准；鉴定结果是人为分析的，人为失误可能会导致鉴定出错。四个选项中A项符合第 三条质疑，故选A。
本题是推理判断题。第五段意思是：DNA指纹颇有价值。如果犯罪嫌疑人不能将自己 的DNA提供给专家，他/她就很可能没有确凿的证据证明自己无罪。由此可以推断出，DNA 指纹对警察破案来说，尤为显得珍贵。故选A。
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