题干

雄性东亚飞蝗体细胞中有23条染色体,均为端着丝粒,其性染色体组成为XO型.雌性蝗虫的性染色体组成为XX型.如图是精巢不同区域细胞分裂中期的图象,有关叙述正确的是(    )

A:图1细胞中的染色体上能发生DNA的复制和转录

B:图1细胞中的染色体数和核DNA数与图2细胞中不相同

C:图2细胞分裂后产生的精子与卵细胞结合后发育的子代均为雌性

D:图2细胞中共有11个四分体,且呈现交叉互换现象

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D

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    A few years ago, my wife, Sue had some serious health problems. She had suffered surgery after surgery and had also put on weight. Diets had not helped her and she suffered constantly from undiagnosed pain. One day the whole family sat down and drew up a “wish list”. To our surprise, one of Sue's items was to run in a marathon. Given her history and physical limitations, I thought her goal was completely unrealistic, but Sue became committed to it.

    She began by running very slowly and every day she ran just a little farther than she did the day before. Soon she could run three miles. Then five. Sue kept practicing and longed to run in the St. George Marathon in southern Utah.

    On the big day, I parked our van near the finish line, waiting for Sue. The rain was steady and the wind was cold. The marathon had started over five hours ago. The fast and strong competitors had finished already. Several cold and injured runners had been transported past me, and I began to panic. The image of Sue, alone and cold, off the road somewhere, made me sick with worry.

    Another hour passed and I spotted a small group running up. As they approached, I could see Sue, in the company of three others, and a woman in her twenties was near Sue. It was obvious that they had become friends during the race. I could see her begin to struggle. But when the finish line came into sight, she confidently even happily picked up her pace the last hundred yards to the finish line. Few people were left to congratulate my wife. They openly praised and embraced her, “She made us believe we could do it,” her new friend stated.

    From then on, she was carrying herself differently. Her head was more upright. Her shoulders were squared. Her walk had a new confidence. Her voice held a new, quiet dignity. It was not as if she had become someone new; it was more as if she had discovered a real self she had not known before. It was perseverance that made her realize she was an undiscovered masterpiece with a million things left to learn about herself. She truly liked her newly discovered self. So did I.