问题 填空题

某种细菌体内某氨基酸(X)的生物合成途径如图:

这种细菌的野生型能在基本培养基(满足野生型细菌生长的简单培养基)上生长,而由该种细菌野生型得到的两种突变型(甲、乙)都不能在基本培养基上生长;在基本培养基上若添加中间产物2,则甲、乙都能生长;若添加中间产物1,则乙能生长而甲不能生长。在基本培养基上添加少量的X,甲能积累中间产物1,而乙不能积累。请回答:

(1)根据上述资料可推论:甲中酶________的功能丧失;乙中酶______的功能丧失,甲和乙中酶_______的功能都正常。由野生型产生甲、乙这两种突变型的原因是野生型的___________(同一、不同)菌体中的不同_______发生了突变,从而导致不同酶的功能丧失。如果想在基本培养基上添加少量的X来生产中间产物1,则应选用_________(野生型、甲、乙)。

(2)将甲、乙混合接种于基本培养基上能长出少量菌落,再将这些菌落单个挑出分别接种在基本培养基上都不能生长。上述混合培养时乙首先形成菌落,其原因是___________。

(3)在发酵过程中,菌体中X含量过高时,其合成速率下降。若要保持其合成速率,可采取的措施是改变菌体细胞膜的________,使X排出菌体外。

答案

(1)b   a   c  不同   基因   甲

(2)甲产生的中间产物1供给乙,使乙能够合成X,保证自身生长产生菌落(答案合理即可)

(3)通透性

选择题
阅读理解

There was a time when the owners of shops and businesses in Chicago had to pay large sums of money to gangsters(匪徒)in return for “protection”. If the money was not paid immediately, the gangsters would quickly put a man out of business by destroying his shop. Getting “protection money” is not a modern means. As long ago as the fourteenth century, an Englishman, Sir John Hawkwood, made the remarkable discovery that people would rather pay large sums of money than have their life work destroyed by gangsters.

Then Sir John Hawkwood arrived in Italy with a group of soldiers and settled near Florence. He soon made a name for himself and came to be known to the Italians as Giovanni Acuto. Whenever the Italian city-states were at war with each other, Hawkwood used to hire his soldiers to those who were willing to pay the high price he demanded.  In times of peace, when business was bad, Hawkwood and his men would march into a city-state and, after burning down a few farms, would offer to go away if protection money was paid to them. Hawkwood made large sums of money with this method. In spite of this, the Italians regarded him as a sort of hero .When he died at eighty, the Florentines gave him a state funeral and had his picture painted, which was in memory of “this bravest man”.

小题1:What protection did Chicago gangsters give to those who paid them?

A.They saved those people’s businesses from destruction.

B.They left those people’s business unharmed much.

C.They sent soldiers to serve them no matter what help they needed willingly.

D.They didn’t take those people’s lives小题2:Sir John Hawkwook's Italian name “Giovanni Acuto” was one which         .

A.he gave himself in order to become better known to the Italians

B.he earned through his sharp practice of selling his ‘protection’

C.he needed so as to hire his soldiers to Italians

D.was given him in telling his services to the others’小题3:The Italians regarded Hawkwood as a sort of hero          .

A.because they couldn’t help admiring his bravery and boldness(胆大)

B.as he aided the citizens in peacetime when business was bad for them

C.he had played an important role in their daily life

D.for he lived so long and was given a state funeral by the Florentines小题4:From the passage, we can guess the gangsters were those         .

A.who were of great importance to the poor

B.who made the businessmen do whatever they were in need of

C.who were always ready to be sent abroad

D.who did harm to others小题5:According to the writer, Hawkwood was           .

A.a sort of national hero

B.an experienced leader

C.a brave soldier

D.a noble gangster