(18分)(选修模块3:现代生物科技专题)
请回答下列与哺乳动物精子和卵子发生有关的问题:
(1)精细胞经变形后,高尔基体发育形成精子的顶体,顶体内含有的___________能协助精子穿过卵母细胞的放射冠和透明带。
(2)某动物排卵时,减数第一次分裂尚未完成,此时卵子处于__________卵母细胞阶段,当该细胞发育至减数第二次分裂___________期时,才具备受精能力。若在卵黄膜和透明带之间看到两个极体,则表明__________过程已完成。
(3)动物的早期胚胎移植到同种且__________与供体相同的动物体内,使之继续发育为新个体的技术叫做胚胎移植。为了获得更多的早期胚胎,常用__________激素对供体进行处理,其目的是获得更多的_________,经人工受精后可得到早期胚胎。用某染料鉴定胚胎细胞是否为活细胞时,发现活胚胎细胞不能被染色,其原因是活细胞膜__________。
(4)若要通过胚胎移植获得遗传物质完全相同的两个新个体,可对发育到桑椹期或囊胚期阶段的早期胚胎进行_________处理,再植入到受体内。若要对早期胚胎进行长期保存,应将其置于__________条件下。
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A. Monday and Tuesday. B. Tuesday and Wednesday.
C. Wednesday and Thursday. D. Monday and Wednesday.
A
I suddenly heard an elephant crying as though frightened. Looking down, I immediately recognized that something was wrong, and ran down to the edge of the near bank. There I saw Ma Shwe with her three-month-old calf struggling in the fast-rising water, and it was a life-and-death struggle. Her calf was floating and screaming with fear. Ma Shwe was as near to the far bank as she could get, holding her whole body against the rushing water, and keeping the calf pressed against her huge body. Every now and then the rushing water would sweep the calf away.
There was a sudden rise in the water and the calf was washed clean over the mother’s body and was gone. Ma Shwe turned quickly to reach it and pressed the calf with her head and trunk(象鼻) against the rocky bank. Then with a huge effort, she picked it up in her trunk and tried until she was able to place it on a narrow shelf of rock.
Just at this moment she fell back into the river. If she were carried down, it would be certain death. I knew, as well as she did, that there was one spot(地点) where she could get up the bank, but it was on the other side from where she had put her calf.
While I was wondering what I could do next, I heard the sound of a mother’s love. Ma Shwe had crossed the river and got up the bank and was making her way back as fast as she could, roaring (吼叫) all the time, but to her calf it was music.
56. The moment the author got down to the river bank he saw _____,
A. the calf was about to fall into the river
B. Ma Shwe was placing the calf on the rock
C. the calf was washed away by the rising water
D. Ma Shwe was holding the calf against the rushing water
A. saved was teachers’ energyB. was teachers’ energy saved
C. teachers’ energy was savedD. was saved teachers’ energy
----_______.
A. No, thanksB. Yes, my pleasure
C. NO, never mind D. Yes, I do
A. Tiring. B. Expensive. C. Enjoyable. D. Quick.