单选题蛋白质溶液的稳定性因素有

单选题原核生物乳糖操纵子受CAP调节，结合并活化CAP的分子是

单选题原核生物转录起始前10 区的核苷酸序列称为

单选题在DNA复制过程中不能催化磷酸二酯键形成的酶是

单选题维系蛋白质三级结构稳定的最重要的键或作用力是

单选题下列结构中，属于蛋白质模体结构的是______。

单选题粪便中主要的色素是

单选题有关RNA聚合酶的叙述，不恰当的是

单选题酸对紫外线的最大吸收峰在哪一波长附近？（）

单选题In 1998 consumers could purchase virtually anything over the Internet. Books, compact discs, and even stocks were available from World Wide Web Sites that seemed to spring up almost daily. A few years earlier, some people had predicted that consumers accustomed to shopping in stores would be reluctant to buy things that they could not see or touch in person. For a growing number of time-starved consumers, however, shopping from their home computer was proving to be a convenient alternative to driving to the store. A research estimated that in 1998 US consumers would purchase $ 7.3 billion of goods over the Internet, double the 1997 total. Finding a bargain was getting easier, owing to the rise of online auctions and Web sites that did comparison shopping on the Internet for the best deal. For all the consumer interest, retailing in cyberspace was still a largely unprofitable business, however. Internet pioneer Amazon. com, which began selling books in 1995 and later branched into recorded music and videos, posted revenue of $153.7 million in the third quarter, up from $37.9 minion in the same period of 1997. Overall, however, the company's loss widened to $45.2 million from $9.6 million, and analysts did not expect the company to turn a profit until 2001. Despite the great loss, Amazon. com had a stock market value of many billions, reflecting investors' optimism about the future of the industry. Internet retailing appealed to investors because it provided an efficient means for reaching millions of consumers without having the cost of operating conventional stores with their armies of salespeople. Selling online carried its own risks, however. With so many companies competing for consumers' attention, price competition was intense and profit margins thin or nonexistent. One video retailer sold the hit movie Titanic for $9.99, undercutting the $19.99 suggested retail price and losing about $6 on each copy sold. With Internet retailing still in its initial stage; companies seemed willing to absorb such losses in an attempt to establish a dominant market position.

单选题下述哪种酶与切除修复无关

单选题 下列哪一选项不是KEGG的子数据库（ ）。 A、KEGG PATHWAY B、KEGG GENOME C、KEGG ORTHOLOGY D、KEGG MEDICINE

单选题真核基因的转录调控

单选题生长因子的作用模式不正确的是

单选题 利用反义核酸阻断基因异常表达的基因治疗方法是 A、基因置换 B、基因替代 C、基因矫正 D、基因失活 E、免疫调节

单选题非竞争性抑制剂对酶促反应的影响表现在

单选题脂肪酸氧化过程中不需要的化合物是

单选题原所以没有活性是因为（）。

单选题蛋白质的变性是由于

单选题DNA的二级结构是( )。