单选题当细菌核糖体亚基在CsCl介质中进行离心时，30S和50S亚基分别变为23S和42S亚基，这是由于除去了某些成分所致，被除去的成分是 a．16S rRNA； b．23S rRNA； c．16S rRNA+23S rRNA； d．蛋白质。

单选题在一个有性生殖的自然种群中，除了具有种群大、没有突变发生、没有新基因加入以及个体间的交配是随机的以外，还需具备下列哪一条件，种群的基因库是稳定的( )。

单选题在真核细胞中tRNA的转录是为 a．RNA pol Ⅰ工负责的； b．RNA pol Ⅱ负责的； c．RNA pol Ⅲ负责的； d．不由任何RNA pol负责。

单选题两个植物自交系，它们的种子重量分别为0.2kg和0.4kg，杂交得到的F1种子为0.3kg，F1×F1杂交产生了1024个植株，4株为0.2kg重的种子，4株为0.4kg重的种子，其他植株的种子重量则介于二者中间，由此可估计决定种子重量的基因约为( )对。

单选题用达尔文的自然选择学说，来判断下列叙述中正确的是( )。

单选题两个植物杂交，它们的种子质量分别是0.02kg，杂交得到的F1代的种子都是0.03kg，自交得1000个植株，4株0.018kg的种子，4株是0.04kg，其他植株的种子质量在这两个极端值之间，那么决定种子质量的基因有( )对。

单选题European farm ministers have ended three weeks of negotiations with a deal which they claim represents genuine reform of the common agricultural policy (CAP). Will it be enough to kick off the Doha world trade negotiations? On the face of it, the deal agreed in the early hours of Thursday June 26th looks promising. Most subsidies linked to specific farm products are, at last, to be broken--the idea is to replace these with a direct payment to farmers, .unconnected to particular products. Support prices for several key products, including milk and butter, are to be cut-that should mean European prices eventually falling towards the world market level. Cut-ting the link between subsidy and production was the main objective of proposals put forward by Mr. Fischler, which had formed the starting point for the negotiations. The CAP is hugely unpopular around the world. It subsidizes European farmers to such an extent that they can undercut farmers from poor countries, who also face trade barriers that largely exclude them from the potentially lucrative European market. Farm trade is also a key feature of the Doha round of trade talks, launched under the auspices of the World Trade Organization (WTO) in November 2001. Developing countries have lined up alongside a number of industrial countries to demand an end to the massive subsidies Europe pays its farmers. Several Doha deadlines have already been missed because of the EU's intransigence, and the survival of the talks will be at risk if no progress is made by September, when the world's trade ministers meet in Cancun, Mexico. But now even the French seem to have gone along with the deal hammered out in Luxembourg. Up to a point, anyway. The package of measures gives the green light for the most eager reformers to move fast to implement the changes within their own countries. But there is an escape clause of sorts for the French and other reform-averse nations. They can delay implementation for up to two years. There is also a suggestion that the reforms might not apply where there is a chance that they would lead to a reduction in land under cultivation. These 1et-outs are potentially damaging for Europe's negotiators in the Doha round. They could significantly reduce the cost savings that the reforms might otherwise generate and, in turn, keep European expenditure on farm support unacceptably high by world standards. Mote generally, the escape clauses could undermine the reforms by encouraging the suspicion that the new package will not deliver the changes that its supporters claim Close analysis of what is inevitably a very complicated package might confirm the sceptics' fears.

单选题对于突变与进化的关系，以下哪种说法最正确?( )

单选题Sanger的双脱氧末端终止法DNA序列测定中不需要下列哪种物质?______

单选题在完全显性、独立遗传且无互作情况下，AaBbcc × AabbCc的后代中与A_B_cc表 现型不同的个体比例为

单选题相互易位杂合体在减数分裂的偶线期和粗线期，四条染色体联会常形成的形象是

单选题某染色体各区段的线性顺序是abc.defg，变成了abd.cefg这叫______。 A．中间缺失 B．顶端缺失 C．臂内倒位 D．臂间倒位

单选题Horse thieves, cattle rustlers, bank robbers, train and stagecoach robbers, highwaymen, murderers, these were but some of the criminals who infested the American frontier during the 19th century. In English legend Robin Hood can be considered a bandit, but the outlaws of the Old West were far more violent men and women without any scruples when it came to taking property or life. The careers of many outlaws have been glamorized through fictional accounts of their deeds and their exploits have been the basis for many movie scripts. The era of the American outlaw lasted about 100 years roughly from 1800 to 1900．There had been lawlessness during the Colonial Era. Frontiers have always attracted misfits, failures and renegades who hope to profit by being beyond the reach of government. In the years just before the Revolutionary War, gangs of horse thieves in the back country of South Carolina were broken up by organized bands of farmers called regulators. As frontier settlement expanded rapidly after the Revolution, more opportunities for criminals opened, two common types of bandits were highwaymen and river pirates. Highwaymen accosted people who traveled on foot or horseback, while river pirates preyed upon the boat traffic on the Ohio, Mississippi, and other rivers. Some bandits engaged in both. Criminals in the West gathered momentum with the gold rushes to California, Idaho, Montana, Nevada, and other states. Stagecoaches and trains carrying gold and money became prime targets for bands of outlaws. Bank robberies emerged after the California Gold Rush of 1849 and as prosperity found its way to frontier towns. The first stage robbery was recorded in 1851, and the first train robbery happened in 1866. After the Civil War there was the growth of the cattle kingdom in Texas and neighboring states. Cattle rustling and horse theft turned into significant operations. Range wars bred a great amount of violence. Cattlemen fought over land and water rights, and they fought with great bitterness against sheep farmers. In Texas, range wars were fought over the use of barbed wire to fence grazing land. By the end of the 19th century, the frontier era was past. Major crime shifted to the cities. Ethnic gangs had existed in the slums for decades, preying mostly on their fellow immigrants. With the arrival of Prohibition in the 1920s, an impetus was given to the formation of organized crime as it exists today.

单选题纯种芦花雄鸡和非芦花母鸡交配，得到子一代。子一代个体互相交配，问子二代的芦花性状与性别的关系是 ____ 。

单选题λ噬菌体侵入大肠杆菌细胞后通过______而进入溶原状态。

单选题现代生物进化论认为：种群是生物进化的基本单位；突变、选择和隔离是新物种形成的基本环节。其中新物种形成的必要条件是( )。

单选题在一个E. coli细胞中同时存在两个lac操纵子，其中一个的操纵基因为野生型(Oo)，另一个的操纵基因为组成突变型(Oc)，则 a．由于Oc的存在，Oo不起作用，即不再结合阻抑物； b．由于Oo的存在，Oc无效，即含Oc的操纵子；也不能结合阻抑物； c．两个操纵子互不影响。

单选题 Vienna was one of the music centers of Europe during the classical period, and Haydn, Mozart, and Beethoven were all active there. As the (1) of the Holy Roman Empire (which included parts of present-day Austria, Germany, Italy, Hungary, Czech and Slovakia), it was a (2) cultural and commercial center (3) a cosmopolitan character. Its population of almost 250,000 (in 1800) made Vienna the fourth largest city in Europe. All three (4) masters were born elsewhere, but they were (5) to Vienna to study and to seek (6) . In Vienna, Haydn and Mozart became close friends and influenced each other's musical (7) . Beethoven traveled to Vienna at sixteen to play for Mozart; at twenty-two, he returned to study with Haydn. Aristocrats from all over the Empire spent the winter in Vienna, sometimes bringing their private (8) . Music was an important part of court life, and a good orchestra was a (9) of prestige. Many of the nobility were excellent musicians. Much music was heard in (10) concerts where aristocrats and wealthy commoners played (11) professional musicians. Mozart and Beethoven often earned money by performing in these intimate concerts. The nobility (12) hired servants who could (13) as musicians. An advertisement in the Vienna Gazette of 1789 (14) : " Wanted, for a house of the gentry, a manservant who knows how to play the violin well. " In Vienna there was also (15) music, light and popular in (16) . Small street bands of wind and string players played at garden parties or under the windows of people (17) to throw (18) money. Haydn and Mozart wrote many outdoor entertainment (19) , (20) they called divertimentos or serenades. Vienna's great love of music and its enthusiastic demand for new works made it the chosen city of Haydn, Mozart and Beethoven.