不同来源的核酸（DNA或RNA）混合物经变性后进行复性时，若这些异源的DNA或RNA之间存在碱基互补的区域，在退火条件下则可形成杂合核酸双链。这种不同来源的单链核酸分子在合适的条件下，通过碱基互补形成双链杂交体的过程称为核酸分子杂交。

DNA双链发生热变性时，A260的变化是

A:升高 B:降低 C:先升高后降低 D:先降低后升高 E:不变

不同来源的核酸（DNA或RNA）混合物经变性后进行复性时，若这些异源的DNA或RNA之间存在碱基互补的区域，在退火条件下则可形成杂合核酸双链。这种不同来源的单链核酸分子在合适的条件下，通过碱基互补形成双链杂交体的过程称为核酸分子杂交。

关于核酸分子杂交，叙述错误的是

A:可以发生在DNA与DNA之间 B:可以发生在RNA与RNA之间 C:可以发生在RNA与DNA之间 D:要求两条单链的碱基完全互补 E:杂交的严格度由反应体系中的盐浓度,温度等决定

类志贺邻单胞菌,埃希菌属的某些血清型,志贺菌属,沙门菌属和耶尔森菌属等均可引起腹泻，但不同菌属引起的腹泻表现各不相同。

引起脓血粪便，并伴有里急后重的病原菌是

A:痢疾志贺菌 B:伤寒沙门菌 C:类志贺邻单胞菌 D:ETEC E:EHEC

DNA Fingerprinting

    DNA is the genetic material found within the cell nuclei of all living things. In mammals the strands of DNA are grouped into structures called chromosomes.¹ With the exception of identical siblings (as in identical twins)²，the complete DNA of each individual is unique.

    DNA fingerprinting is sometimes called DNA typing.³ It is a method of identification that compares bits of DNA. A DNA fingerprint is constructed by first drawing out a DNA sample from body tissue or fluid such as hair, blood, or saliva. The sample is then segmented using enzymes, and the segments are arranged by size. The segments are marked with probes and exposed on X-ray film，where they form a pattern of black bars — the DNA fingerprint.⁴ 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 diseases⁵，it soon came to be used in criminal investigations and legal affairs. The first criminal conviction based on DNA evidence⁶ in the United Statesoccurred in 1988. In criminal investigations, DNA fingerprints derived from evidence collected at the crime scene are compared to the DNA fingerprints of suspects. Generally, courts have accepted the reliability of DNA testing and admitted DNA test results 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.

词汇：

figerprinting /ˈfɪŋgəprɪnt/ n. 指纹法，指纹术 

nucleus /"nju:klɪəs/ n. 核，中心
genetic / dʒəˈnetɪk / adj. 遗传的 

mammal /ˈmæml/ n. 哺乳动物
chromosome /ˈkrəʊməˌsəʊm/ n. 染色体 

identification /"aɪˌdentɪfɪˈkeɪʃn/ n. 识别，鉴定，证明
enzyme /"enzaɪm/ n. 酶 

suspect /səˈspekt/ n. 嫌疑犯
fingerprint / ˈfɪŋgəprɪnt / n. 指纹 

saliva /səˈlaɪvə/ n. 唾液
segment /ˈsegmənt/ vt.  分割，分裂；切片，不笨
controversial / ˌkɒntrəˈvɜ:ʃl / adj. 有争议的 

uniform /"ju:nɪfɔ:ml/ adj. 一致的，相同的

注释：

1.In mammals the strands of DNA are grouped into structures called chromosomes.哺乳L动物的 DNA线被组合为称作染色体的各种结构。
2.With the exception of identical siblings (as in identical twins)：生物姊妹体除外（如完全相同的双胞胎）
3.DNA fingerprinting is sometimes called DNA typing. DNA 指纹检查法有时也称 DNA 印记法。
4.The segments are marked with probes and exposed on X-ray film, where they form a pattern of black bars - the DNA fingerprint.切片先用探针做标记，然后在X光片上曝光。胶片上形成 由黑色条纹组成的图案，这就是DNA指纹。
5.Originally used to detect the presence of genetic diseases ： (DNA 指纹法）开始是用来探测遗传病的存在
6.The first criminal conviction based on DNA evidence：基于 DNA 提供证据的首例定罪

Some people believe that using a DNA fingerprint may not be so reliable because____

A:the accuracy of DNA fingerprinting has been challenged B:no private laboratory follows uniform testing standards or quality controls C:mistakes are possible when researchers explain the results of their tests D:suspects may not have enough money to provide their own DNA to law-courts

DNA Fingerprinting

    DNA is the genetic material found within the cell nuclei of all living things. In mammals the strands of DNA are grouped into structures called chromosomes.¹ With the exception of identical siblings (as in identical twins)²，the complete DNA of each individual is unique.

    DNA fingerprinting is sometimes called DNA typing.³ It is a method of identification that compares bits of DNA. A DNA fingerprint is constructed by first drawing out a DNA sample from body tissue or fluid such as hair, blood, or saliva. The sample is then segmented using enzymes, and the segments are arranged by size. The segments are marked with probes and exposed on X-ray film，where they form a pattern of black bars — the DNA fingerprint.⁴ 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 diseases⁵，it soon came to be used in criminal investigations and legal affairs. The first criminal conviction based on DNA evidence⁶ in the United Statesoccurred in 1988. In criminal investigations, DNA fingerprints derived from evidence collected at the crime scene are compared to the DNA fingerprints of suspects. Generally, courts have accepted the reliability of DNA testing and admitted DNA test results 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.

词汇：

figerprinting /ˈfɪŋgəprɪnt/ n. 指纹法，指纹术 

nucleus /"nju:klɪəs/ n. 核，中心
genetic / dʒəˈnetɪk / adj. 遗传的 

mammal /ˈmæml/ n. 哺乳动物
chromosome /ˈkrəʊməˌsəʊm/ n. 染色体 

identification /"aɪˌdentɪfɪˈkeɪʃn/ n. 识别，鉴定，证明
enzyme /"enzaɪm/ n. 酶 

suspect /səˈspekt/ n. 嫌疑犯
fingerprint / ˈfɪŋgəprɪnt / n. 指纹 

saliva /səˈlaɪvə/ n. 唾液
segment /ˈsegmənt/ vt.  分割，分裂；切片，不笨
controversial / ˌkɒntrəˈvɜ:ʃl / adj. 有争议的 

uniform /"ju:nɪfɔ:ml/ adj. 一致的，相同的

注释：

1.In mammals the strands of DNA are grouped into structures called chromosomes.哺乳L动物的 DNA线被组合为称作染色体的各种结构。
2.With the exception of identical siblings (as in identical twins)：生物姊妹体除外（如完全相同的双胞胎）
3.DNA fingerprinting is sometimes called DNA typing. DNA 指纹检查法有时也称 DNA 印记法。
4.The segments are marked with probes and exposed on X-ray film, where they form a pattern of black bars - the DNA fingerprint.切片先用探针做标记，然后在X光片上曝光。胶片上形成 由黑色条纹组成的图案，这就是DNA指纹。
5.Originally used to detect the presence of genetic diseases ： (DNA 指纹法）开始是用来探测遗传病的存在
6.The first criminal conviction based on DNA evidence：基于 DNA 提供证据的首例定罪

This essay talks about DNA fingerprinting concerning the following aspects EXCEPT____

A:legal application of the method B:the way to obtain a DNA sample C:work yet to be done about DNA fingerprinting D:possible danger in drawing a DNA sample from the human body

RNA与DNA生物合成相同的是（）

A:需RNA引物 B:以3＇→5’方向DNA为模板 C:两条模板链同时合成 D:新链生成的方向5’→3’ E:形成3’，5’-磷酸二酯键

一个DNA分子复制完毕后，新形成的DNA分子单链通常是（）

A:DNA母链的一个片段 B:和母链DNA相同，但T被U取代 C:和DNA母链之一完全相同 D:和DNA母链稍有不同

DNA基因有两条链，与mRNA序列相同(除T代替U外)的链叫做

A:模板链 B:编码链 C:重链 D:cDNA链

DNA基因有两条链，与mRNA序列相同(除T代替U外)的链叫做

A:模板链 B:编码链 C:重链 D:cDNA链