试题与答案

摩尔根用一只白眼突变体的雄性果蝇进行一系列杂交实验后,证明了基因位于染色体上。其

题型:选择题

题目:

摩尔根用一只白眼突变体的雄性果蝇进行一系列杂交实验后,证明了基因位于染色体上。其系列杂交实验过程中,最早获得白眼雌果蝇的途径是[ ]

A.亲本白眼雄果蝇×亲本雌果蝇

B.F1白眼雄果蝇×F1雌果蝇

C.F2白眼雄果蝇×F1雌果蝇

D.F2白眼雄果蝇×F3雌果蝇

答案:

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题型:阅读理解

阅读理解

     A Brown University sleep researcher has some advice for people who run high schools : Don't start

classes so early in the morning. It may not be that the students who nod off at their desks are lazy. And

it may not be that their parents have failed to enforce (确保) bedtime. Instead, it may be that biologically

these sleepyhead students aren't used to the early hour.

     " Maybe these kids are being asked to rise at the wrong time for their bodies, " says Mary Carskadon,

a professor looking at problems of adolescent  (青春期的) sleep at Brown's School of Medicine.

     Carskadon is trying to understand more about the effects of early school time in adolescents. And , at

a more basic level, she and her team are trying to learn more about how the biological changes of

adolescence affect sleep needs and patterns.

     Carskadon says her work suggests that adolescents may need more sleep than they did at childhood ,

no less,as commonly thought.

     Sleep patterns change during adolescence, as any parent of an adolescent can prove. Most

adolescents prefer to stay up later at night and sleep later in the morning. But it's not just a matter of choice-their bodies are going through a change of sleep patterns.

     All of this makes the transfer from middle school to high school-which may start one hour earlier in

the morning-all the more difficult , Carskadon says. With their increased need for sleep and their

biological clocks set on the "sleep late , rise late"  pattern, adolescents are up against difficulties when it

comes to trying to be up by 5 0r 6 a. m. for a 7 : 30 a. m. first bell. A short sleep on a desktop may be

their bodies' way of saying,"l need a timeout. "

1. Carskadon suggests that high schools should not start classes so early in the morning because_______.

A. it is really tough for parents to enforce bedtime

B. it is biologically difficult for students to rise early

C. students work so late at night that they can't get up early

D. students are so lazy that they don't like to go to school early

2. The underlined phrase " nod off"  ( Paragraph l) most probably means"__________".

A. turn around                    

B. agree with others

C. fall asleep                      

D. refuse to work

3. What might be a reason for the hard transfer from middle school to high school? __________

A. Adolescents depend more on their parents.

B. Adolescents have to choose their sleep patterns.

C. Adolescents sleep better than they did at childhood.

D. Adolescents need more sleep than they used to.

4. What is the text mainly about? _________

A. Adolescent heath care.

B. Problems in adolescent learning.

C. Adolescent sleep difficulties.

D. Changes in adolescent sleep needs and patterns.

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