将大肠杆菌在含有15N标记的培养液中培养后，再转移到含有14N的普通培养液中培养

发布时间：2017-05-05 17:05 │ 来源：www.tikuol.com

题型：选择题

问题：

将大肠杆菌在含有¹⁵N标记的培养液中培养后，再转移到含有¹⁴N的普通培养液中培养，10小时后提取DNA分子进行分析，得出含¹⁵N的DNA分子占总DNA分子的比例为l/16，则大肠杆菌的细胞周期是[ ]

A．1小时

B．1.5小时

C．2.0小时

D．4.0小时

考点：DNA的复制

题型：选择题

Mail-order Advertisement

Moonlight Company Products for a Sale Environment
A2477-HAND SOAP You are going to love this natural soap. There are no chemicals in it .It is very good for your hands and face.		D4545-MICROBIAL INSECTICIDE Insects （昆虫）are going to run away from our new microbial insecticide （环保杀虫剂）.It is safe and natural
B2377-HOME CLEANER You are not going to need 5 or 6 chemical cleaners. You have Dr Clean! It is safe and strong ,and it cleans everything in your house !		A2104-CANVAS BAG（帆布袋） You are going to say ,“No paper or plastic!”You have this excellent heavy canvas shopping bag
item	code		Price
Natural shampoo	T6762		$3.00
Microbial insecticide	D4545		$2.50
Canvas bag	A2104		$4.00
Hand soap	A2477		$1.00
Home cleaner	B2377		$2.23
Postage :$3.50

根据材料内容选择最佳答案，并将其标号填入题前括号内。
小题1:What do you need if you want to kill ants?

A．Microbial insecticide.	B．Moonlight Company.
C．Canvas Bag.	D．Dr Clean.

小题2:You're going to love the natural soap, because ____ .

A．it is clean	B．ii smells sweet
C．there are no chemicals	D．it is powerful

小题3:How much will you pay if you want three shampoos and two canvas bag mailed to you?

小题4:What does the underlined word "it' most probably refer to?

A．Canvas bag.

小题5:How many products are mentioned in the ads ?

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题型：选择题

药物经济学的主要任务是（）

A.对比分析与评价不同的药物治疗方案所产生的相对经济效果

B.对比分析与评价药物治疗与其他治疗方案所产生的相对经济效果

C.对比分析与评价不同厂家生产药物所产生的相对经济效果

D.为合理用药、药政管理、新药的研究和开发提供决策依据

E.从社会角度考虑如何合理分配使用有限的卫生资源和医药经费

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题型：选择题

哥伦布从美洲返回欧洲，若想一路顺风顺水，则所借助的盛行风为______________，所借助的洋流是______________，按洋流成因分类应属______________流。

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题型：选择题

影响舵效的主要因素是（）

①舵角大小；

②流经舵面的流速；

③船的转动惯性及纵横倾；

④风流、浅水等海况；

⑤舵机的性能。

A.①～④

B.②～⑤

C.①③④⑤

D.①～⑤

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题型：选择题

I heard Susan surprised her teacher by working hard. Yes,（）

A.her teacher worked hard.

B.Susan worked hard.

C.the teacher was surprising.

D.Susan was surprised.

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