第2题: [单项选择]What is the main thought expressed in this appeal A. The museums are a financial success. B. People are leaving New York too rapidly. C. The public should support cultural institutions. D. Crocker Band wants new depositors. 参考答案:C
第3题: [单项选择]乳糖操纵子中I基因编码产物是 A. 乙酰基转移酶 B. 透酶 C. β半乳糖苷酶 D. 一种阻遏蛋白 E. 一种激活蛋白 参考答案:D 答案解析:[解题思路] I基因编码一种阻遏蛋白,它与操纵序列O结合,从而阻遏操纵子于关闭状态。 [命题规律] 考察“原核基因表达调控”。必须掌握。