问题
选择题
下列不属于染色体变异的是[ ]
A．人第5号染色体的短臂缺失
B．同源染色体的非姐妹染色单体之间的交叉互换
C．人第21号染色体增加了一条
D．果蝇第Ⅱ号染色体上某片段移接到第Ⅲ号染色体上
答案
答案：B
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下列不属于染色体变异的是[ ]
A．人第5号染色体的短臂缺失
B．同源染色体的非姐妹染色单体之间的交叉互换
C．人第21号染色体增加了一条
D．果蝇第Ⅱ号染色体上某片段移接到第Ⅲ号染色体上
答案：B
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| It was the district sports meet. My foot still hadn't healed (痊愈) from a(n) 1 injury. I had 2 whether or not I should attend the meet. But there I was, 3 for the 3,000-meter run. " Ready … set …" The gun popped and we were off. The other girls rushed 4 me. I felt 5 as I fell farther and farther behind. " Hooray!" shouted the crowd. It was the loudest 6 I had ever heard at a meet. The first-place runner was two laps (圈) ahead of me when she crossed the finish line. " Maybe I should 7 ," I thought as I moved on. 8 , I decided to keep going. During the last two laps, I ran 9 and decided not to 10 in track next year. It wouldn't be worth it, 11 my foot did heal. When I finished, I heard a cheer- 12 than the one I'd heard earlier. I turned around and 13 , the boys were preparing for their race." They must be cheering for the boys." I was leaving 14 several girls came up to me. " Wow, you've got courage!" one of them told me. " Courage? I just 15 a race!" I thought. " I would have given up on the first lap," said another girl." We were cheering for you. Did you hear us?" Suddenly I regained 16 . I decided to 17 track next year. I realized strength and courage aren't always 18 in medals and victories, but in the 19 we overcome (战胜). The strongest people are not always the people who win, 20 the people who don't give up when they lose. | ||||
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