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在大肠杆菌中，碱性磷酸酯酶(APase)由基因phoA编码。如果把APase所催化的反应产物磷酸盐加入细胞培养物，在生长中细胞的APase的合成明显受到抑制。还有两种其他基因phoB和phoR似乎也参与phoA表达的调节；phoB中的突变导致在磷酸盐存在或不存在的条件下APase合成的减少。phoR中的突变导致APase呈组成型的合成(见表10-2-24)。我们知道phoB和phoR基因各产生一种蛋白质，所以表10-2-24中所示的突变不代表顺式作用的突变。我们也知道phoA基因是受到转录控制的调节。假定除了上述蛋白质外，没有其他蛋白质或小分子参与调节phoA基因。 表10-2-24 突变体 在磷酸盐存在与否时，APase的相对浓度 无 有 phoA + phoB + phoR + phoA - phoB + phoR + phoA + phoB - phoR + phoA + phoB + phoR - phoA + phoB - phoR - 100 0 0 100 5 20 0 1 100 5
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参考答案：
举一反三
【单选题】I have called the station and they told me the next train for Dalian ________at 3∶10.
A.
will leave
B.
left
C.
has left
D.
leaves
查看完整题目与答案
【单选题】肠源性紫绀是以下哪种食物中毒的典型症状？( )
A.
亚硝酸盐中毒
B.
砷中毒
C.
有机磷农药中毒
D.
细菌性中毒
E.
组胺中毒
查看完整题目与答案
【单选题】某机床厂生产销售精密机床，同时经营一家非独立核算的饭店，它属于(    )。
A.
混合销售行为    
B.
一般销售行为
C.
兼营非应税劳务行为    
D.
视同销售行为
查看完整题目与答案
【单选题】________ the alien was in the museum, I called the TV station.
A.
Because
B.
Then
C.
As soon as
D.
While
查看完整题目与答案
【简答题】根据要求改写句子。 1. I called the TV station while the alien was eating pizza. (改为否定句) I _________ _________ the TV station while the alien was eating pizza. 2. I was talking to the reporter when the alien ca...
查看完整题目与答案
【单选题】I have called the station and they told me the next train for Beijing _______ at 8:10.
A.
will leave
B.
has left
C.
leaves
D.
left
查看完整题目与答案
【简答题】Pair 4 4.1 When I saw the smoke, I called the fire station to ask them to come immediately. 4.2 When I saw the smoke, I called the fire station to ask the ______ to come immediately.
查看完整题目与答案
【简答题】I called the station to about train times.remain, top, peril, unearth, matter,inquire, consistent, mode, granted, until
查看完整题目与答案
【判断题】定时 / 计数器 1 使用时必须 使 用单片机的 T0 脚 ( P3.5 )
A.
正确
B.
错误
查看完整题目与答案
【单选题】I have called the station and they told me the next train for Da Lian _____ at 3:10．
A.
will leave
B.
left
C.
has left
D.
leaves
查看完整题目与答案
相关题目：
【单选题】I have called the station and they told me the next train for Dalian ________at 3∶10.
A.
will leave
B.
left
C.
has left
D.
leaves
查看完整题目与答案
【单选题】肠源性紫绀是以下哪种食物中毒的典型症状？( )
A.
亚硝酸盐中毒
B.
砷中毒
C.
有机磷农药中毒
D.
细菌性中毒
E.
组胺中毒
查看完整题目与答案
【单选题】某机床厂生产销售精密机床，同时经营一家非独立核算的饭店，它属于(    )。
A.
混合销售行为    
B.
一般销售行为
C.
兼营非应税劳务行为    
D.
视同销售行为
查看完整题目与答案
【单选题】________ the alien was in the museum, I called the TV station.
A.
Because
B.
Then
C.
As soon as
D.
While
查看完整题目与答案
【简答题】根据要求改写句子。 1. I called the TV station while the alien was eating pizza. (改为否定句) I _________ _________ the TV station while the alien was eating pizza. 2. I was talking to the reporter when the alien ca...
查看完整题目与答案
【单选题】I have called the station and they told me the next train for Beijing _______ at 8:10.
A.
will leave
B.
has left
C.
leaves
D.
left
查看完整题目与答案
【简答题】Pair 4 4.1 When I saw the smoke, I called the fire station to ask them to come immediately. 4.2 When I saw the smoke, I called the fire station to ask the ______ to come immediately.
查看完整题目与答案
【简答题】I called the station to about train times.remain, top, peril, unearth, matter,inquire, consistent, mode, granted, until
查看完整题目与答案
【判断题】定时 / 计数器 1 使用时必须 使 用单片机的 T0 脚 ( P3.5 )
A.
正确
B.
错误
查看完整题目与答案
【单选题】I have called the station and they told me the next train for Da Lian _____ at 3:10．
A.
will leave
B.
left
C.
has left
D.
leaves
查看完整题目与答案
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