单选题大多数基因表达调控的最基本环节是( ) A．复制水平 B．转录水平 C．转录起始水平 D．转录后加工水平 E．翻译水平
单选题下面不属于含硫氨基酸的是
单选题DNA复制时需要解开DNA的超螺旋结构，参与此过程的酶是
A.DNA polⅠ
B.DNA polⅡ
C.DNA polⅢ
D.端粒酶
E.拓扑异构酶
单选题用碱裂解法提取质粒DNA时，染色体DNA之所以被除去，是因为( ) A．染色体DNA断成了碎片 B．染色体DNA分子量大，而不能释放 C．染色体变性后来不及复性 D．染色体未同蛋白质分开而沉淀 E．以上都是
单选题A．氢键断裂B．肽键断裂C．疏水键断裂D．盐键断裂E．构象变化
单选题A．异戊巴比妥B．铁螯合剂C．COD．二硝基苯酚
单选题体内调节氧化磷酸化的基本因素是
单选题关于V-src病毒癌基因叙述正确的是
A.存在于DNA病毒基因组中
B.来源于Rous肉瘤病毒
C.癌基因产物为受体型酪氨酸蛋白激酶
D.是第一个被证实的病毒癌基因
E.引起体外培养的细胞发生恶性转化
单选题下列病毒中哪一个属于正链RNA病毒?
单选题下列属于芳香氨基酸的是
单选题人类基因组完全图谱的公布是在( )年2月12日。
单选题原核生物基因转录终止子在终止点前均有( )。
单选题下面关于真核生物翻译的叙述中，哪一个是正确的?( )
单选题在转录过程中，三种真核RNA聚合酶都需要的转录因子是：
单选题制作可摘局部义齿印模，选择的托盘与牙弓内外侧应有多大间隙
单选题研究得最早的核酸分子杂交种类是( ) A．菌落杂交 B．Southern杂交 C．Northern杂交 D．液相杂交 E．原位杂交
单选题利用几根毛发进行基因诊断主要体现了基因诊断的哪项特点( ) A．高特异性 B．应用广泛性 C．高灵敏性 D．早期诊断性 E．唯一性
单选题基因诊断的目标分子不可以是( ) A．DNA B．基因的表达产物 C．RNA D．脂多糖 E．mRNA
单选题The use of chemicals in almost all areas of life has become a commonplace phenomenon. There is growing evidence, however, that chemicals in the environment, including pesticides, may contribute to some illnesses. While studies are still being conducted, preliminary conclusions point to the verdict that such chemicals are indeed negatively impacting those humans to whom they are exposed. Children are especially vulnerable to toxic substances. Pound for pound, they eat, drink and breathe more than adults, all of which exposes them more heavily to those chemicals to which most individuals encounter on a daily basis. Furthermore, their bodies are still in developing stages, exacerbating the negative effects of those chemicals, which negatively impact them. Of 50 types of pesticides commonly used in American schools, a study conducted by the National Coalition Against the Misuse of Pesticides found that many caused negative reactions in laboratory animals. Such negative effects included kidney and liver damage, cancer, and neurological and reproductive problems. These implications of these findings are far-reaching. Given the variety of harmful effects attributed to those pesticides tested, one must pause and consider whether it is wise to continue their use in the nation's schools, where children will be constantly exposed to them. Activists have lobbied for the elimination of such use with a degree of success, and recent findings, if supported by further analysis and confirmation, may help further the cause. A long term solution or alternative, however, remains elusive. In the short run, however, there may be some measures that can be taken to mitigate the harmful effects of dangerous pesticides. The American Medical Association's Council on Scientific Affairs concluded in a 1997 report that given the "particular uncertainty.., regarding the long-term health effects of low-dose pesticide exposures," it is "prudent" for adults and children to limit their exposure and to "consider the use of the least toxic chemical pesticides or non-chemical alternatives. /
单选题基因克隆中能特异切割DNA的酶是( ) A．限制性核酸内切酶 B．DNA聚合酶Ⅰ C．DNA聚合酶Ⅰ大片段 D．DNA连接酶 E．碱性磷酸酶