2014年職稱英語真題:職稱英語考試衛(wèi)生A試題

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    第四十五篇 DNA Fingerprinting【DNA指紋】
    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. With the exception of identical siblings (as in 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 DN A. A DAN 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. 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 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.
    1. According to the essay, we can find chromosomes
    A. in a fish.
    B. in a tree.
    C. in a sheep.
    D. in a rock.
    2. DNA fingerprinting is more often used for
    A. obtaining samples of chromosomes.
    B. providing evidence in court investigations.
    C. proving the horse to be a mammal.
    D. printing books about biology.
    3. When your brother looks exactly like you, your complete DNA may be
    A. exactly like his.
    B. totally different from his.
    C. unique.
    D. lost.
    4. 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 what have come of their tests.
    D. suspects may not have enough money to provide their own DNA to law-courts.
    5. 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.
    DNA指紋
    DNA是所有生物細(xì)胞核子發(fā)現(xiàn)的基因材料。哺乳動物的DNA線被組合為稱作染色體的各種結(jié)構(gòu)。除生物姊妹體外(如完全相同的雙胞胎),每一個體的整條DNA是獨一無二的。
    DNA指紋有時也稱作DNA印記法。這是一種通過比較少量DNA的鑒別方法。DNA指紋的構(gòu)成先要從身體組織或液體中抽取DNA標(biāo)本,如頭發(fā)、血液或唾液。采取的標(biāo)本用酶分割成若干部分,各切片根據(jù)大小排列。切片先用探針做標(biāo)記,然后曝光于X光片上。膠片上形成由黑色條紋組成的圖案,這就是DNA指紋。若兩個不同標(biāo)本的DNA指紋完全相像,則這兩個標(biāo)本可能來自同一人。
    DNA指紋首次作為鑒別技術(shù)進(jìn)行開發(fā)是在1985年。開始是用來探測遺傳疾病的,很快便被應(yīng)用于刑事調(diào)查與法律事務(wù)?;贒NA所提供證據(jù)的首例定罪是1988年,在美國。在刑事調(diào)查中,把從犯罪現(xiàn)場采集的證據(jù)中提取的DNA村本與犯罪嫌疑人的相比。一般說來,法庭已承認(rèn)DNA測試的可靠性并允許DNA測試結(jié)果納為證據(jù)然而,在一些方面DNA指紋頗具爭議性:結(jié)果的精確性,測試成本及技術(shù)的錯誤使用的可能性。
    由于一些原因,DNA指紋的精確性受到了挑戰(zhàn)。首先,由于是DNA切片而并非完整的DNA被作為指紋進(jìn)行研究;DNA指紋可能并非獨一無二的;尚未進(jìn)行過大規(guī)模研究以證實DNA指紋測試結(jié)果是獨一無二的。此外,DNA指紋常是在私人實驗室作的,可能并不遵循統(tǒng)一的測試標(biāo)準(zhǔn)與質(zhì)量控制。再有,既然必須由人來解釋測試,人為的錯誤可能導(dǎo)致錯誤結(jié)果。
    DNA指紋頗為昂貴。如果犯罪嫌疑人不能將自己的DNA提供給專家,他/她就很可能沒有確鑿的證據(jù)證明自己無罪。為鑒定目的而作的DNA測試的廣泛使用可能會導(dǎo)致DNA指紋數(shù)據(jù)庫的建立。
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