单选题达尔文认为，生物进化是( )。

单选题Who won the World Cup 1994 football game? What happened at the United Nations? How did the critics like the new play? (1) an event takes place, newspapers are on the streets (2) the details. Wherever anything happens in the world, reporters are on the spot to (3) the news. Newspapers have one basic (4) , to get the news as quickly as possible from its source, from those who make it to those who want to (5) it. Radio, telegraph, television, and (6) inventions brought competition for newspaper. So did the development of magazines and other means of communication. (7) , this competition merely spurred the newspapers on. They quickly made use of the newer and faster means of communication to improve the (8) and thus the efficiency of their own operations. Today more newspapers are (9) and read than ever before. Competition also led newspapers to branch out into many other fields. Besides keeping readers (10) of the latest news, today's newspapers (11) and influence readers about politics and other important and serious matters. Newspapers influence readers' economic choices (12) advertising. Most newspapers depend on advertising for very (13) . Newspapers are sold at a price that (14) even a small fraction of the cost of production. The main (15) of income for most newspapers is commercial advertising. The (16) in selling advertising depends on a newspaper's value to advertisers. This (17) in terms of circulation. How many people read the newspaper? Circulation depends (18) on the work of the circulation department and on the services or entertainment (19) in a newspaper's pages. But for the most part, circulation depends on a newspaper's value to readers as a source of information (20) the community, city, county, state, nation, and world—and even outer space.

单选题单倍体链孢霉一般是粉红色的，白色是它的突变型，如果把粉红色链孢霉与白色链孢霉进行杂交，其子代是粉红色的概率是______

单选题玉米n+1的花粉不育，n+1的胚囊可育，已知R产生红色，r无色。在杂交RRr♀×rr♂中子代的表现型比例是______。 A．1红:1无 B．3红:1无 C．5红:1无 D．6红:1无

单选题一个女人的父亲是色盲，她的兄弟中有两人和一个舅舅是血友病患者如果这个女人有一个血友病的患儿，则她的基因型必定是什么?( )

单选题E. coli DNA polymerase Ⅰ具有3′→5′和5′→3′外切核酸酶活性，这两种酶活性的区别在于 a．3′→5′活性只切割碱基配对处的二酯键；b．5′→3′活性只切割碱基不配对处的二酯键； c．3′→5′活性只切割碱基不配对处的二酯键； d．两种活性对切割处的碱基配对与否无选择，只是5′→3′活性一次只切除一个核苷酸。

单选题在豚鼠中，黑毛对白毛是显性，如果基因库中90%是显性基因B，10%是隐性基因b，则种群中基因型BB、Bb、bb的频率分别是( )。

单选题变异是生命的基本特征之一，细菌产生可遗传的变异来源于( )。

单选题关于自然选择，以下叙述错误的是( )。

单选题菌株A可以石油燃料为营养，菌株B则不能利用石油燃料，活化菌株B，杀死菌株A，混合在一起，几小时后，混合物变得混浊，经检查得知，混浊是菌株A快速生长的结果，引起的这种现象原因是______ A．性导 B．转录 C．转导 D．转化

单选题关于数量性状的描述，正确的有______。 A.由多个基因控制 B.一般不受环境影响 C.呈现不连续变异 D.差别非常明显，“非此即彼”

单选题荷兰科学家底·弗里斯(Hugo de Vries)把另外两位科学家的理论(或学说)联系到了一起，这两位科学家是( )。

单选题假如具有相等的加性效应的两对基因(AABB)影响某品种玉米的高度。把平均1.8m的高型品种和平均0.6m的矮型品种杂交，如果矮品种的高度归因于基因型(aabb)，那么，每个基因的效应是多少?( )

单选题果蝇中某一X连锁基因杂合时，表现缺刻翅，纯合致死，雌性缺刻翅个体与正常翅雄性个体进行杂交，下列哪种组合子代表现型是正确的______

单选题有一个杂交组合aaBB×AAbb，下列有关其F1的陈述正确的是______。 A.若位点间不连锁，产生Ab配子时，同样可产生AB配子 B.若位点间紧密连锁，与不连锁相比，F1的表型分布不同 C.若位点间紧密连锁，与不连锁相比，F2的表型分布不同 D.上述答案都不对

单选题杂合体中，呈现两个基因(一对基因)效应的现象称为______

单选题DNA聚合酶Ⅲ的描述中哪项不正确?( )

单选题影响基因频率的因素是( )。

单选题转录的启始反应方程为(箭头只表示顺序)，其中R=RNApol，P=promoter，RPc=closedbinarycomplex，RPo=opencomplex，RPi·RNA=ternarycomplex。在这些步骤中a．1是可逆反应；b．2是可逆反应；c．3是可逆反应；d．1，2，3均不是可逆反应。

单选题Holliday中间体在( )过程中产生。