问题
单项选择题
DNA分子经过诱变，某位点上的一个正常碱基（设为P）变成了尿嘧啶，该DNA连续复制两次，得到的4个子代DNA分子相应位点上的碱基对分别为U-A、A-T、G-C、C-G，推测“P”可能是（）
A.胸腺嘧啶
B.腺嘌呤
C.胸腺嘧啶或腺嘌呤
D.胞嘧啶
答案
参考答案：D
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DNA分子经过诱变，某位点上的一个正常碱基（设为P）变成了尿嘧啶，该DNA连续复制两次，得到的4个子代DNA分子相应位点上的碱基对分别为U-A、A-T、G-C、C-G，推测“P”可能是（）
A.胸腺嘧啶
B.腺嘌呤
C.胸腺嘧啶或腺嘌呤
D.胞嘧啶
参考答案：D
Joe loved to eat hamburgers in fast food restaurants with his friend Daniel. Every week, they would go to eat hamburgers. One day, Joe a dream. In his dream, there was a very big hamburger. And there was a voice said, "Eat it! It is !" So Joe took this big hamburger and began to eat. But suddenly Joe felt sick and had a serious stomachache. When he looked around for help, he saw in a mirror. He became very fat! "No!" Joe shouted and from the terrible dream. He ran to the bathroom quickly if he became fat in real life. The dream made Joe think if he had a healthy habit. The next day, Joe and Daniel went to eat hamburgers as usual(像往常一样). Joe stopped at the door of the restaurant and said, "Daniel, if we keep eating so hamburgers, we will get fat or sick. Shall we eat today?" Daniel said, "Of course. Why do you change(改变) your mind today?" "I think fast food isn't all bad. But we shouldn't eat them too often," said Joe. that day, they began to eat fewer hamburgers and more healthy food.
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