问题
单项选择题
下列关于SD序列的说法正确的是( )。
A．SD序列对真核生物和原核生物的翻译都是重要的
B．SD序列相对于起始密码子AUG而言，是与方向和位置都无关的
C．SD序列有时会隐藏在mRNA茎-环结构中，对翻译起到抑制作用
D．原核生物中的编码基因的翻译共同受到一个上游SD序列的控制
答案
参考答案：C
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下列关于SD序列的说法正确的是( )。
A．SD序列对真核生物和原核生物的翻译都是重要的
B．SD序列相对于起始密码子AUG而言，是与方向和位置都无关的
C．SD序列有时会隐藏在mRNA茎-环结构中，对翻译起到抑制作用
D．原核生物中的编码基因的翻译共同受到一个上游SD序列的控制
参考答案：C
| Every group has a culture, however uncivilized it may seem to us. To the professional anthropologist, there is no intrinsic superiority of one culture over another, just as to the professional linguist, there is no intrinsic hierarchy among languages. People once thought of the languages of backward groups as undeveloped. While it is possible that language in general began as a series of grunts and groans, it is a fact established by the study of "backward" languages that no spoken tongue answers that description today. Most languages of uncivilized groups are, by our most severe standards, extremely complex. They differ from Western languages not in their sound patterns or grammatical structures, which usually are fully adequate for all language needs, but only in their vocabularies, which reflect the objects and activities known to their speakers. Even in this aspect, two things are to be noted. First, all languages seem to possess the machinery for vocabulary expansion, either by putting together words already in existence or by borrowing them from other languages and adapting them to their own system. Second, the objects and activities requiring names and distinctions in "backward" languages, while different from the West, are often surprisingly numerous and complicated. A Western language distinguishes merely between two degrees of remoteness ("this" and "that"). But some languages of the American Indians distinguish between what is close to the speaker, or to the person addressed, or removed from both, or out of sight, or in the past, or in the future. |
To the professional linguists,______.
A．there is no intrinsic superiority of cultures
B．there is no intrinsic hierarchy of languages
C．all languages came from grunts and groans
D．all languages are most severe and standard