单选题下列不是蛋白质二级结构的构象形式

单选题下列除哪项外，其他代谢途径均不能在成熟红细胞中进行

单选题关于蛋白质变性后的哪一种说法是正确的

单选题以下序列构成的DNA双螺旋，在相同条件下热变性，再缓慢冷却进行复性，复性最快的序列是：______。 A.ATATATAT B.AATAATAA C.AAATTATT D.AAAATTTT

单选题含有Ⅲ型内含子的RNA拼接过程中，第一次转酯反应发生时，分支位点上突出的腺苷酸上核糖与5"拼接位点的磷酸基团连接的方式是：

单选题关于westem印迹，不正确的叙述是______ A.从细胞中提取蛋白质 B.经电泳分离并转移到膜上 C.应用特异的检测抗体 D.标记的DNA探针与转移到膜上的蛋白质杂交 E.检测基因的表达

单选题染色体不分离发生在第一次卵裂，则形成的嵌合体具有的细胞系的数目是( )。

单选题在lac操纵子中，cAMP结合的是 A.lac阻遏蛋白 B.CAP C.RNA聚合酶 D.β-半乳糖苷酶 E.乙酰基转移酶

单选题下列化合物中，除哪个外都是异戊二烯的衍生物?______

单选题活性甲基的供体是

单选题合成脂肪酸的限速酶为

单选题体内合成脂肪酸的氢来自

单选题不是细胞间信息物质的是

单选题嘧啶核苷酸从头合成途径中合成的第一个脱氧嘧啶核苷酸是

单选题将两段寡聚脱氧核苷酸片段5'-CAGACCACGTAAGGGATC-3'和5'-CTTAC-3'与DNA聚合酶一起加到含有dATP、dGTP、dCTP和dTTP的反应混合物之中，预测反应的终产物中被掺入的各碱基的比例是： A．1G:2C:1A:1T B．4G:1C:3T C．4G:2C:1A:5T D．3G:1C:2T

单选题In a perfectly free and open market economy, the type of employer -- government or private -- should have little or no impact on the earnings differentials between women and men. However, if there is discrimination against one sex, it is unlikely that the degree of discrimination by government and private employers will be the same. Differences in the degree of discrimination would result in earnings differentials associated with the type of employer. Given the nature of government and private employers, it seems most likely that discrimination by private employers would be greater. Thus, one would expect that, if women are being discriminated against, government employment would have a positive effect on women's earnings as compared with their earnings from private employment. The results of a study by Fuchs support this assumption. Fuchs's results suggest that the earnings of women in an industry composed entirely of government employees would be 14. 6 percent greater than the earnings of women in an industry composed exclusively of private employees, other things being equal. In addition, both Fuchs and Sanborn have suggested that the effect of discrimination by consumers on the earnings of self-employed women may be greater than the effect of either government or private employer discrimination on the earnings of women employees. To test this hypothesis, Brown selected a large sample of White male and female workers from the 1970 Census and divided them into three categories: private employees, government employees, and self-employed. (Black workers were excluded from the sample to avoid picking up earnings differentials that were the result of racial disparities. ) Brown's research design controlled for education, labor-force participation, mobility, motivation, and age in order to eliminate these factors as explanations of the study's results. Brown's results suggest that men and women are not treated the same by employers and consumers. For men, self-employment is the highest earnings category, with private employment next and government lowest. For women, this order is reversed. One can infer from Brown's results that consumers discriminate against self-employed women. In addition, self-employed women may have more difficulty than men in getting good employees and may encounter discrimination from suppliers and from financial institutions. Brown's results are clearly consistent with Fuchs's argument that discrimination by consumers has a greater impact on the earnings of women than does discrimination by either government or private employers. Also, the fact that women do better working for government than for private employers implies that private employers are discriminating against women. The results do not prove that government does not discriminate against women. They do, however, demonstrate that if government is discriminating against women, its discrimination is not having as much effect on women's earnings as is discrimination in the private sector.

单选题转录激活蛋白的作用是______ A.识别和结合启动子 B.激活结构基因的转录 C.原核和真核生物均有 D.与RNA聚合酶结合起始转录 E.属于负调控的转录因子

单选题原核细胞信使RNA含有几个其功能所必需的特征区段，它们是：

单选题关于糖蛋白的叙述，错误的是

单选题血浆中的胆固醇酯是______。