单选题二倍体中维持配子正常功能的最低数目的染色体称______。 A．染色体组 B．单倍体 C．二倍体 D．多倍体
单选题两个植物杂交，他们的株高分别是30cm和50cm，杂交得到的F1代的株高都是40cm，F1×F1杂交产生2010个植株，有8株株高在30cm，8株的株高为50cm，其他植株的株高在这两个极端值之间，那么，决定该植株的株高的基因有______。 A．6对 B．5对 C．4对 D．3对
单选题生物繁殖的基本单位是( )。
单选题一个______生物配子所含有的全套染色体就是一个染色体组。 A．单倍体 B．二倍体 C．整倍体 D．单体
单选题最早用果蝇为材料发现性连锁遗传的科学家是______，发现果蝇的X染色体不分离现象并直接证明遗传的染色体学说的科学家是______。
单选题假定在一个植物群体内，有两对基因Aa和Bb决定植株高度，效应是累加的，纯合体AABB株高为50cm，而aabb为30cm，则这两个个体杂交的F1植株高度大约为______cm。 A．50 B．40 C．30 D．20
单选题某个体发生了性细胞的隐性突变，在后代中，突变性状的表现和出现突变纯合体是______。 A．第一代表现，第二代纯合 B．第二代表现，第二代纯合 C．第一代表现，第一代纯合 D．第二代表现，第三代纯合
单选题22，原核启动子在-35和-10处有两个中心，-10处的序列对DNA解链有重要作用，此处
a．富A-T； b．富G-C； c．A-T/G-C各半。
单选题真核细胞液中的mRNA通常是
a．monocistronic； b．polycistronic； C．intercistronic。
单选题苯丙酮尿症是一种隐性纯合的严重的代谢缺陷病症，基因位于常染色体上。如果两个正常的双亲，生了一个患病的女儿，一个正常表型的儿子，那么儿子是此病基因携带者的概率是______
单选题如果在第三代中雄性1与雌性4交配，它们的第一个子代是淡黄毛的概率是______
单选题染色体结构变异中的缺失和重复在染色体配对中都形成环(瘤)，但这两种变异形成的环所涉及的染色体是不同的，其中缺失环涉及______。 A．缺失染色体 B．部分重复染色体 C．正常染色体 D．缺失和正常染色体交换
单选题在一个链霉素抗性的Hfr菌株中，已知A位点比B位点先转移，而Strs位点最后转移，用菌株HfrA+B+Strs与F-A-B-StrR菌株接合，经一定时间用搅拌器中断接合，添加链霉素，然后分析活菌的基因型，各种基因型如下：A-B-=80%
A+B+=10% A+B-=50%
A-B+=5%，从这些资料看，A和B之间的重组率应是______
A.10%
B.20%
C.50%
D.33.3%
E.上述答案均不对
单选题一个表型正常的人，其舅父患某种常染色体隐性遗传病，他如果和表型正常的姨表妹结婚，后代中患该病的风险是______。
单选题一条雌鲫鱼一年内能繁殖约3000余条幼鱼，但能够生存下来并发育成熟的却很少，按照达尔文进化观点，这个实例说明了( )。
单选题生物进化的内在因素是( )。
单选题A very important world problem, if not the most serious of all the great world problems which affect us at the moment, is the increasing number of people who actually inhabit this planet. The limited amount of land and land resources will soon be unable to support the huge population if it continues to grow at its present rate. In an early survey conducted in 1888, a billion and a half people inhabited the earth. Now, the population exceeds five billion and is growing fast--by the staggering figure of 90 million in 1988 alone. This means that the world must accommodate a new population roughly equal to that of the United States and Canada every three years! Even though the rate of growth has begun to slow down, most experts believe the population size will still pass eight billion during the next 50 years. So why is this huge increase in population taking place? It is really due to the spread of the knowledge and practice of what is becoming known as "Death Control". You have no doubt heard of the term "Birth Control"--" Death Control" is something rather different. It recognizes the work of the doctors and scientists who now keep alive people who, not very long ago, would have died of a variety of then incurable diseases. Through a wide variety of technological innovations that include farming methods and sanitation, as well as the control of these deadly diseases, we have found ways to reduce the rate at which we die--creating a population explosion. We used to think that reaching seventy years old was a remarkable achievement, but now eighty or even ninety is becoming recognized as the normal life-span for humans. In a sense, this represents a tremendous achievement for our species. Biologically this is the very definition of success and we have undoubtedly become the dominant animal on the planet. However, this success is the very cause of the greatest threat to mankind. Man is constantly destroying the very resources which keep him alive. He is destroying the balance of nature which regulates climate and the atmosphere, produces and maintains healthy soils, provides food from the seas, etc. In short, by only considering our needs of today, we are ensuring there will be no tomorrow. An understanding of man's effect on the balance of nature is crucial to be able to find the appropriate remedial action. It is a very common belief that the problems of the population explosion are caused mainly by poor people living in poor countries who do not know enough to limit their reproduction. This is not true. The actual number of people in an area is not as important as the effect they have on nature. Developing countries do have an effect on their environment, but it is the populations of richer countries that have a far greater impact on the earth as a whole. The birth of a baby in, for example, Japan, imposes more than a hundred times the amount of stress on the world's resources as a baby in India. Most people in India do not grow up to own cars or air-conditioners--nor do they eat the huge amount of meat and fish that the Japanese child does. Their life-styles do not require vast quantities of minerals and energy. Also, they are aware of the requirements of the land around them and try to put something back into nature to replace what they take out. For example, tropical forests are known to be essential to the balance of nature yet we are destroying them at an incredible rate. They are being cleared not to benefit the natives of that country, but to satisfy the needs of richer countries. Central American forests are being destroyed for pastureland to make pet food in the United States cheaper; in Papua New Guinea, forests are destroyed to supply cheaper cardboard packaging for Japanese electronic products; in Burma and Thailand, forests have been destroyed to produce more attractive furniture in Singapore and Japan. Therefore, a rich person living thousands of miles away may cause more tropical forest destruction than a poor person living in the forest itself. In short then, it is everybody's duty to safeguard the future of mankind--not only through population control, but by being more aware of the effect his actions have on nature. Nature is both fragile and powerful. It is very easily destroyed; on the other hand, it can so easily destroy its most aggressive enemy--man.
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______。
单选题在一个隔离的岛上住着5800个人，其中2800人是男性。有196个男性患有红绿色盲。该色盲是由于伴X隐性突变因子(r)造成的。该色盲不影响个体的健康。在该岛上至少有一个女性患此种色盲的可能性是多少?
单选题下表是T4噬菌体5个表型相似的突变体的互补实验结果(+、-分别表示能和不能互补)，试根据结果判断他们分属于几个顺反子?______ 1 2 3 4 5 1 - + + + + 2 - + - + 3 - + - 4 - + 5 - A．2 B．3 C．4 D．5