单选题设某一植物中的两个连锁位点之间交换值为21%，如果检查了这两位点间的交叉时记录了150个孢母细胞，则应该有______个孢母细胞会在这两位点间形成交叉。 A．21 B．42 C．63 D．84

单选题mRNA核苷酸顺序的3′→5′分别相应于蛋白质氨基酸顺序的 a．N端-C端； b．C端-N端； c．与N端、C端无对应关系。

单选题紫茉莉枝条有绿色、白色和花斑3种类型，在花斑×绿色的杂交组合中，子代将______。 A．只有花斑枝条 B．只有白色枝条 C．有绿色、白色、花斑3种枝条 D．只有绿色枝条

单选题酵母DNA的A+T/G+C为2，则A/G、A/C、A/T应分别为______。

单选题原始的原核生物的新陈代谢类型最可能的是( )。

单选题在独立遗传下，杂种AaBbDdEe自交，后代中基因型全部纯合的个体占______。 A．25% B．1/8 C．1/16 D．9/64

单选题正反交结果一致的遗传方式有 ____ 。

单选题人工选择之所以能选育出新品种，自然选择之所以能形成新物种，其共同的选择基础是( )。

单选题某人是一个常染色体基因的杂合子Bb，而他带有一个隐性的X连锁基因d。在他的精子中有多大比例带有bd基因? (a)0； (b)1/2； (c)1/8； (d)1/16； (e)1/4。

单选题Back in the 1870s, Charles Darwin's cousin Francis Galeton wanted to define the face of a criminal. He assembled photographs of men convicted of heinous crimes and made a composite by lining them up on a single photographic plate. The surprise: everybody liked the villain, including Galton himself. He reasoned that the villainous irregularities he supposed belonged to criminal faces had disappeared in the averaging process. In the next century, scientists began to show reliably that faces combined digitally on computers were likable—more so than the individual faces from which they were composed. Although people clearly admire the long legs of Brazilian model Ana Hickmann or Dolly Parton's breasts, in general humans like averages. Researchers confirmed that humans judge real faces by their differences or similarities from a norm. But they also found that the norm can change quickly: When researchers showed 164 people sets of 100 computer-generated faces representing a slow transition from male to female—and from Japanese to Caucasian—it turned out that the test subjects' idea of what constitute an "average" face shifted depending on the first face they saw. When they were flashed a super masculine face first, more faces on the spectrum impressed them, by contrast, as female. The masculine face had, in effect, set a standard. From then on, other faces had to be more masculine in order to rate as belonging to the gender. The study noted a similar shift using a scale of faces moving from surprise to disgust. The authors, who published their results in the journal Nature, conclude that in real life we also quickly change ore" perception of the midpoint—what's normal—depending on what we see. We may not be aware that our judgment has changed; we simply see differently, says Michael Webster, a psychologist at the University of Nevada in Reno and coauthor of the study. One implication is that individual and social attitudes toward what's acceptable, and what's beautiful, change over time. "If you look at plastic-surgery trends, in the 1950s and 1960s you saw little upturned noses," notes Harvard psychologist Nancy Etcoff, author of the book Survival of the Prettiest : The Science of Beauty. "Now the noses are broader and the lips are plumper. We're seeing images from around the globe, and it's changing our idea of the average. " So if you're unhappy with some aspect of your face, take comfort: beauty is a moving target.

单选题tRNA的反密码子能识别mRNA的密码子。反密码子的第一碱基能识别一个以上的密码子第三碱基(wobbling)者为 a．A； b．A和C； c．U和G； d．C。

单选题入噬菌体的裂解途径是由以下哪个蛋白基因控制? ____ 。

单选题原核mRNA的Shine-Dalgarno顺序通常是 a．多嘧啶序列； b．多嘌呤序列； c．嘌呤和嘧啶基本各半。