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  3. DNA sequences from some of the most deadly pathogens(病原体)known to man can be

DNA sequences from some of the most deadly pathogens(病原体)known to man can be

游客2023-07-05  51
问题     DNA sequences from some of the most deadly pathogens(病原体)known to man can be bought over the Internet, the Guardian has discovered.
    In an investigation which shows the ease with which terrorist organizations could obtain the basic ingredients of biological weapons, this newspaper obtained a short sequence of smallpox(天花)DNA. The deadly virus has existed only in laboratories since being eradicated from the world’ s population 30 years ago.
    The DNA sequence of smallpox, as well as other potentially dangerous pathogens such as poliovirus and 1918 flu are freely available in online public databases. So to build a virus from scratch, a terrorist would simply order consecutive lengths of DNA along the sequence and glue them together in the correct order. This is beyond the skills and equipment of the kitchen chemist, but could be achieved by a well-funded terrorist with access to a basic lab and PhD-level personnel.
    One study estimated that because most people on the planet have no resistance to the extinct virus, an initial release which infected just 10 people would spread to 2.2 million people in 180 days.
    The DNA sample we ordered had, at our request, three small modifications to render it harmless before it was sent by post to a residential address in London. The company has conceded that it was not aware it was sending out a sequence of modified smallpox DNA.
    There are legitimate reasons for researchers to buy lengths of DNA from pathogens, for example in developing treatments or vaccines against them. However, because this industry is so new and unregulated, companies are selling custom-made DNA without making thorough checks on the identities of the people who are placing the orders or what the sequences are.
    Of the four main companies operating in the UK, none currently screens all their DNA orders. There are 39 companies operating in North America and not all screen their orders. [br] The underlined word "consecutive" in the 3rd paragraph means______.
选项 A、serial
B、equal
C、different
D、same
答案 A
解析 词汇题。由题干可定位到第三段…order consecutive lengths of DNA…根据下文中along the sequence…(依照序列)并分析语义可知此处consecutive应表示连续长度的DNA。故答案选A。
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