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【单选题】
组织理论上把管理层次多而管理宽度小的结构称之为( )。A.
直式结构
B.
扁平结构
C.
直线结构
D.
矩形结构
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【多选题】What are the functions of reverse transcriptases?
A.
Reverse transcriptases catalyze three different reactions: (1) RNAdependent DNA synthesis, (2) RNA degradation, and (3) DNA-dependent DNA synthesis. Like many DNA and RNA polymerases, reverse transcriptases contain Zn 2+ .
B.
Each transcriptase is most active with the RNA of its own virus, but each can be used experimentally to make DNA complementary to a variety of RNAs. The DNA and RNA synthesis and RNA degradation activities use separate active sites on the protein. For DNA synthesis to begin, the reverse transcriptase requires a primer, a cellular tRNA obtained during an earlier infection and carried in the viral particle.
C.
This tRNA is base-paired at its 3′ end with a complementary sequence in the viral RN The new DNA strand is synthesized in the 5′ → 3′ direction, as in all RNA and DNA polymerase reactions. Reverse transcriptases, like RNA polymerases, do not have 3′ → 5′ proofreading exonucleases.
D.
They generally have error rates of about 1 per 20,000 nucleotides added. An error rate this high is extremely unusual in DNA replication and seems to be a characteristic of most enzymes that replicate the genomes of RNA viruses. A consequence is a higher mutation rate and faster rate of viral evolution, which is a factor in the frequent appearance of new strains of disease-causing retroviruses.
【单选题】根据《建设工程工程量清单计价规范》(GB 50500—2008)的规定，下列选项中，不属于按设计图示尺寸以面积计算墙面镶贴块料的是( )。
A.
石材墙面
B.
碎拼石材墙面
C.
装饰板墙面
D.
块料墙面
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