2002年,严重呼吸系统困难症(SARS)疫情在中国广东首次被发现,逐渐扩散至东南亚乃至全球,引发了一场全球性的传染病疫情。下列关于引起该疾病的SARS致病原--SARS病毒描述正确的是:
A. SARS病毒的遗传物质是由核糖核酸组成,属于RNA病毒
B. SARS病毒的遗传物质是由脱氧核糖核酸组成,属于DNA病毒
C. SARS病毒的复制基于逆转录过程
D. SARS病毒的基因表达主要是基于RNA转录过程
E. SARS病毒的基因表达主要是基于DNA复制过程
查看答案
真核生物的转录前起始复合物(PIC)是指:
A. RNA聚合酶与TATAAT序列
B. RNA聚合酶与CAAT序列结合
C. 各种转录因子互相结合后再与RNA聚合酶、DNA模板结合
D. α因子与RNA聚合酶全酶结合
E. α因子与RNA聚合酶核心酶结合
It was not until December 25 ________ we finally heard from him.
A. which
B. that
C. when
D. then
Don't ________ other people's problems and make them your own.
A. get involved in
B. is involved in
C. be involved in
D. ge involved on
He didn't go to the World Park because he ___________ there twice.
A. has been
B. had been
C. has gone
D. had gone
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