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在某一精母细胞中,有一对染色体中一个单体的基因顺序为 1234 。 5678 ,另一个为 1265 。 4378 (中间的“。”表示着丝粒)。如果在减数分裂时在 3 和 4 之间发生了一次交换,在它所形成的四个配子中,这个染色体的构成分别是
- A.1234 。 56781256 。34218734 。5678 1265 。4321
- B.1234 。 56781256 。43788734 。5612 1256 。4321
- C.1234 。 56781265 。43218734 。5678 1265 。4378
- D.1234 。 56781265 。43211234 。5678 8765 。4387
通读下面和短文,然后在后面所给的四个选英中,选出一个最佳答案.
Bill and Fred were students at a university (大学) and they were friends. They didn't have 1 , so when it was time 2 their holidays, Bill said,“Let's take our holidays in a trailer (拖车), Fred. It's cheaper than a hotel. I can 3 my father's trailer. ”Fred was very happy, so they got into the trailer to begin their 4 .
They wanted to get up 5 to go fishing, but they didn't have an alarm clock (闹钟).
“That's all right, Bill,” Fred said. “I'll put these small pieces of bread 6 the top of the trailer tonight and they'll 7 in the morning.”
Bill was very 8 , but he didn't say anything.
Fred was right. 9 the day broke, small birds came down to eat the bread, and their 10 woke up Bill and Fred very quickly.
1.A.any money |
B.much money |
C.little money |
D.many money |
[ ] |
2.A.to |
B.with |
C.for |
D.take |
[ ] |
3.A.lend |
B.borrow |
C.for |
D.take |
[ ] |
4.A.holidays |
B.work |
C.practice |
D.play |
[ ] |
5.A.the next day early |
B.early the next day |
C.late the next day |
D.the next day late |
[ ] |
6.A.in |
B.under |
C.on |
D.beside |
[ ] |
7.A.wake up us |
B.wake |
C.wake up |
D.wake us up |
[ ] |
8.A.happy |
B.surprised |
C.unhappy |
D.nice |
[ ] |
9.A.Before |
B.If |
C.As soon as |
D.Then |
[ ] |
10.A.sound |
B.noise |
C.singing |
D.words |
[ ] |