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【单选题】
土鳖虫药材是A.
鳖蠊科昆虫地鳖或冀地鳖的雌虫干燥体
B.
鳖蠊科昆虫地鳖或冀地鳖的雄虫干燥体
C.
芫青科昆虫地鳖或冀地鳖的雄虫干燥体
D.
鳖科昆虫地鳖或冀地鳖的雌虫干燥体
E.
芫青科昆虫地鳖或冀地鳖的雌虫干燥体
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【简答题】某公路上有一面大镜子，从镜子中看到汽车的车辆的号码如图 所示， 则该汽车的号码是（ ）。
【多选题】How is thymidylate derived from dCDP and dUMP?
A.
DNA contains thymine rather than uracil, and the de novo pathway to thymine involves only deoxyribonucleotides. The immediate precursor of thymidylate (dTMP) is dUMP. In bacteria, the pathway to dUMP begins with formation of dUTP, either by deamination of dCTP or by phosphorylation of dUDP. The dUTP is converted to dUMP by a dUTPase. The latter reaction must be efficient to keep dUTP pools low and prevent incorporation of uridylate into DN
B.
Conversion of dUMP to dTMP is catalyzed by thymidylate synthase. A one-carbon unit at the hydroxymethyl (–CH 2 OH) oxidation level is transferred from N 5 , N 10 -methylenetetrahydrofolate to dUMP, then reduced to a methyl group.
C.
The reduction occurs at the expense of oxidation of tetrahydrofolate to dihydrofolate, which is unusual in tetrahydrofolate-requiring reactions.
D.
The dihydrofolate is reduced to tetrahydrofolate by dihydrofolate reductase—a regeneration that is essential for the many processes that require tetrahydrofolate. In plants and at least one protist, thymidylate synthase and dihydrofolate reductase reside on a single, bifunctional protein.
【单选题】专门规范人类生殖技术和精子库的伦理文件是
A.
《人类辅助生殖技术和人类精子库伦理原则》
B.
《人类辅助生殖技术管理办法》
C.
《人类精子库管理办法》
D.
《人类辅助生殖技术规范》
【简答题】演示技能是生物学教学中常用的教学技能,结合初中生物教材中绿色植物的蒸腾作用的相关内容,完成一个演示设计。
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