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______。

单选题脂肪酸氧化的限速酶是

单选题血糖浓度低时，脑仍能摄取葡萄糖而肝不能是因为( )(2005年)

单选题下列载体中对外源DNA片段的容量最大的是( )。

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

单选题如果食物中长期缺乏植物油，将导致人体内减少的物质

单选题Like all quintessentially British things, gardening is a pastime that has long been in decline. From a high point of ￡5 billion in 2001, spending on plants, tools and garden furniture has fallen every year since then, to around ~3 billion in 2008．The arrival of economic recession only deepened the gloom: to credit-crunched consumers, shrubs and hanging baskets seemed obvious candidates for cuts. Yet the latest figures from the Horticultural Trades Association (HTA) suggest a bumper year for garden-related expenditure is in the making. Sales volumes were up by 21% in March and 28% in April compared with the same months a year earlier. This was not the result of deep discounting, a strategy that many other retailers have been adopting. The value of garden goods sold was 37% higher in March and 42% higher in April than a year earlier, whereas the value of all sales had increased by just 3% in April. Datamonitor, a market-research firm, reckons that gardening will continue to outperform the rest of retailing for at least the next two years. Much of the good news is due to the weather, admits Tim Briercliffe, the HTA's director of business development. Last year the vital spring months were damp and miserable; this year sunshine (and weathermen's prediction of a hot summer) has boosted custom. But the economic downturn itself has turned out to be as much a blessing as a curse. Gardening may be a luxury, argues Mr. Briercliffe, but it competes with other, more expensive luxuries. "People who might have otherwise booked a city break to Prague are staying at home and making the best of what they have," he maintains. According to Ipsos MORI, a pollster, three-quarters of people plan to spend at least as much on their garden this year as last. Economic hardship has created a new breed of gardener too. Partly, that reflects people making the most of their enforced leisure: "We get some unemployed city types who are just filling time while looking for another job," admits a garden-centre worker near the London commuter town of Guilford. But there are more positive developments. Much of the growth in garden spending has come from the under-35s, not traditionally a green-fingered demographic. One explanation is that environmentalism and thriftiness have made growing vegetables trendy, an idea that is supported by growing shortage of allotments. But there is more to it than pleasant weather and belt-tightening. The HTA detects deeper, and darker, changes in the national psyche. Citing research from the Future Foundation, a prognosticatory consultancy, it reckons that people are spending more time in their homes, fortifying them into havens from an unwelcoming world haunted by crime, bureaucracy and rising unemployment. The longer the downturn persists, the greener the grass may grow.

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( )。

单选题纤维状蛋白的主要构象形式是什么?______。

单选题在基因治疗中基因转移的生物学方法是以什么作为基因转移系统( ) A．质粒载体 B．病毒载体 C．脂质体 D．黏粒 E．肿瘤细胞

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A．叶酸类似物B．AMP类似物C．dUMP类似物D．嘧啶类似物E．氨基酸类似物

单选题当前在基因治疗研究中，研究者倾向于使用的载体是______。 A．质粒 B．腺病毒 C．噬菌体 D．YAC

单选题 SD序列与下列哪种rRNA相互作用 A、5S B、23S C、16S D、5.8S E、18S

单选题酶之所以能加速反应速度，并不是因为______。

单选题以下哪种病毒是二倍体RNA基因组( ) A．SARS冠状病毒 B．HBV C．HIV D．SV40 E．流感病毒H1N1

单选题决定酶促反应特异性的是(　　　)

单选题通过同源重组，将目的基因导入特定的细胞，矫正原有的缺陷基因，这种基因治疗策略是( ) A．基因修饰 B．基因添加 C．基因干预 D．基因置换 E．基因添加

单选题下列关于伴刀豆球蛋白A-琼脂糖的应用，哪一项是正确的?______