单选题关于前导链叙述正确的是

单选题下列关于DNA的双螺旋二级结构稳定的因素中，哪一项是不正确的?______

单选题关于真核生物DNA分子中基因排布特点的叙述中错误的是

单选题下列哪种抑制剂对原核生物和真核生物的蛋白质合成均有抑制作用?

单选题载脂蛋白的主要结构特征是含有较多的

单选题从侵入细菌到溶菌不同感染阶段，噬菌体基因的表达表现为( )。

单选题染色体中遗传物质的主要化学成分是______ A.组蛋白 B.非组蛋白 C.DNA D.RNA E.mRNA

单选题当大量的RNA与有限的DNA杂交时( )。

单选题下列哪种碱基不存在于DNA中

单选题载体蛋白顺浓度梯度转运Na + 入胞的同时，将葡萄糖逆浓度梯度一起带入胞内，此转运方式为______。

单选题下列载体中对外源DNA片段的容量最大的是( )。

单选题纤维状蛋白的主要构象形式是什么?______。

单选题插入因子是提高什么频率的诱变剂?______ A.转换 B.颠换 C.缺失 D.移码突变

单选题A．血液酸碱度B．二氧化碳分压C．缓冲碱D．标准碳酸氢盐E．实际碳酸氢盐

单选题具有二硫键的二十元环多肽激素是______。

单选题哪种情况会导致移码突变______ A.倒位 B.颠换 C.插入一个碱基 D.连续缺失三个碱基 E.以上都不对

单选题The Supreme Court will hear arguments about the use of public money for the private schooling of children with special needs. It's interesting to note what's not at issue: namely, that when a public school system is unable to provide an appropriate education, it is obligated to pay the costs of private school. Too bad poor children don't have that unshakable right; if they did, there would be no controversy about the District program that gives vouchers to low-income children to attend private schools. The case to be heard by the court hinges on whether parents have to enroll a child with special needs in public school before the child can attend private school at public expense. Special-education advocates say students shouldn't have to waste time before being placed in a setting that best suits their needs, while school boards worry about a ruling that could amount to an unfettered fight to private schooling at public expense. What strikes us about the emotionally charged debate is the acceptance by both sides that sometimes it is appropriate to use public money to pay for a child to go to a private school. So, why all the arguments about the approximately$14 million for a federally funded program that lets 1,700 D. C. students attend private schools instead of failing public schools? To hear critics of the D. C. Opportunity Scholarship Program tell it, the use of public money for private schooling is as unprecedented as it is undesirable. In addition to the billions of dollars spent annually on private school tuitions for students with disabilities, private schools get public money for books, technology and teacher training. As long as the money is seen as benefiting the child, it is considered a proper, even desirable, use of public dollars. Don't get us wrong. We're not arguing for the unilateral right of parents to enroll their sons and daughters in any school they wish with the taxpayers picking up the bill. Abuse of special-education policies has contributed to increased costs that threaten to take needed money from general public education funds. Safeguards are needed. Public schools should be pressed to do a better job for students with disabilities and students without. But there are schools in Washington where statistics show that failure is almost guaranteed. If a school system can't educate a child—whether because of acute special needs or its own historical failings—why should that child not have options for a " free appropriate public education " ?

单选题磷酸戊糖途径的生理意义，不包括

单选题不以胆固醇为原料的化合物是

单选题逆转录病毒基因组复制时所用的引物为______ A.RNA B.DNA C.tRNA D.mRAN E.不用引物