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接合中假如受体细胞接受了F因子,受体细胞有可能变成供体细胞。

提问人:网友qyjwhq 发布时间:2022-01-06
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更多“接合中假如受体细胞接受了F因子,受体细胞有可能变成供体细胞。”相关的问题
第1题
接合时F因子进入受体细胞,受体细胞()。

A. 经历裂解

B. 快速繁殖

C. 变成供体细胞

D. 发育出线粒体

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第2题
F+ⅹF-接合中,F+的F因子转移到F-中去了。因而原来的F+变成了F-,使原来的F-变成了F+。
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第3题
生长因子受体的组成分为 ()

A、细胞内部的配体亲和部分

B、细胞内部的酪氨酸激酶结合部位

C、细胞膜的连接部位

D、细胞外部的配体亲和部分

E、线粒体的连接部位

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第4题
转化:受体菌直接摄取供体菌游离的DNA片段,从而获得新的性状。
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第5题
培养细胞用的培养基配置后一般进行高压灭菌。
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第6题

Go through the passage “Body Language” within 1 minute, and answer the question that follows. (Tips: Read the first sentence of each paragraph.) Body Language What does scientific literature tell us about the idea that body language reflects our real feelings? One experiment carried out about 10 years ago by Ross Buck from Carnegie-Mellon University in Pennsylvania suggests that spontaneous facial expression is not a very good index of real emotional state. Buck and his colleagues tested the accuracy with which people could identify the emotions felt by another person. They presented one set of subjects with color slides involving a variety of emotionally-loaded visual stimuli - such as "scenic" slides (landscapes, etc), "maternal" slides (mothers and young children), disgusting slides (severe facial injuries and burns) and unusual slides (art objects). Unknown to these subjects, they were being televised and viewed by another matched set of subjects, who were asked to decide, on the basis of the televised facial expressions, which of the four sets of slides had just been viewed. This experiment involved both male and female pairs, but no pairs comprising both men and women; that is men observed only men, and women observed women. Buck found that the female pairs correctly identified almost 40 per cent of the slides used - this was above the level which would be predicted by chance alone. (Chance level is 25 per cent here, as there were four classes of slide). But male pairs correctly identified only 28 per cent of slides - not significantly above chance level. In other words, this study suggests that facial expression is not a very good index of "real" feeling - and in the case of men watching and interpreting other men, is almost useless. Paul Ekman from the University of California has conducted a long series of experiments on nonverbal leakage (or how nonverbal behavior may reveal real inner states) which has yielded some more positive and counter-intuitive results. Ekman has suggested that nonverbal behavior may indeed provide a clue to real feelings and has explored in some detail people actively involved in deception, where their verbal language is not a true indication of how they really feel. Ekman here agrees with Sigmund Freud, who was also convinced of the importance of nonverbal behavior in spotting deception when he wrote: "He that has eyes to see and ears to hear may convince himself that no mortal can keep a secret. If his lips are silent, he chatters with his finger-tips; betrayal oozes out of him at every pore." Ekman predicted that the feet and legs would probably hold the best clue to deception because although the face sends out very quick instantaneous messages, people attend to and receive most feedback from the face and therefore try to control it most. In the case of the feet and legs the "transmission time" is much longer but we have little feedback from this part of the body. In other words, we are often unaware of what we are doing with our feet and legs. Ekman suggested that the face is equipped to lie the most (because we are often aware of our facial expression) and to "leak" the most (because it sends out many fast momentary messages) and is therefore going to be a very confusing source of information during deception. The legs and feet would be the primary source of nonverbal leakage and hold the main clue to deception. The form the leakage in the legs and feet would take would include "aggressive foot kicks, flirtatious leg displays, abortive restless flight movements". Clues to deception could be seen in "tense leg positions, frequent shifts of leg posture, and in restless or repetitive leg and foot movements." Ekman conducted a series of experiments to test his speculations, some involving psychiatric patients who were engaging in deception, usually to obtain release from hospital. He made films of interviews involving the patients and showed these, without sound, to one of two groups of observers. One group viewed only the face and head, the other group, the body from the neck down. Each observer was given a list of 300 adjectives describing attitudes, emotional state, and so on, and had to say which adjectives best described the patients. The results indicated quite dramatically that individuals who utilized the face tended to be misled by the patients, whereas those who concentrated on the lower body were much more likely to detect the real state of the patients and not be misled by the attempted deception. These studies thus suggest that some body language may indeed reflect our real feelings, even when we are trying to disguise them. Most people can, however, manage to control facial expression quite well and the face often seems to provide little information about real feeling. Paul Ekman has more recently demonstrated that people can be trained to interpret facial expression more accurately but this, not surprisingly, is a slow laborious process. Ekman's research, suggests that the feet and legs betray a great deal about real feelings and attitudes but the research is nowhere near identifying the meanings of particular foot movements. Ray Birdwhistell of the Eastern Pennsylvania Psychiatric Institute has gone some way towards identifying some of the basic nonverbal elements of the legs and feet, and as a first approximation has identified 58 separate elements. But the meanings of these particular elements are far from clear and neither are the rules for combining the elements into larger meaningful units. Perhaps in years to come we will have a "language" of the feet provided that we can successfully surmount the problems described earlier in identifying the basic forms of movement following Birdwhistell's pioneering efforts, of how they may combine into larger units, and in teaching people how they might make sense of apparently contradictory movements. In the meantime, if you go to a party and find someone peering intently at your feet - beware. ********************************************************* Question: What does this passage want to tell the readers?

A、Researchers have developed a thorough knowledge about body language.

B、Spontaneous facial expression is not a very good index of real emotional state.

C、Some body language may indeed reflect people’s real feelings.

D、The study of body language is a newly emerged subject.

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第7题

Read the passage "The Discovery of X-rays" quickly and choose the paragraph(s) which contain(s) the answer(s). You may choose more than one answer for question 3. The Discovery of X-rays Par. 1 Except for a brief description of the Compton effect, and a few other remarks, we have postponed the discussion of X-rays until the present chapter because it is particularly convenient to treat X-ray spectra after treating optical spectra. Although this ordering may have given the reader a distorted impression of the historical importance of X-rays, this impression will be corrected shortly as we describe the crucial role played by X-rays in the development of modern physics. Par. 2 X-rays were discovered in 1895 by Roentgen while studying the phenomena of gaseous discharge. Using a cathode ray tube with a high voltage of several tens of kilovolts, he noticed that salts of barium would fluoresce when brought near the tube, although nothing visible was emitted by the tube. This effect persisted when the tube was wrapped with a layer of black cardboard. Roentgen soon established that the agency responsible for the fluorescence originated at the point at which the stream of energetic electrons struck the glass wall of the tube. Because of its unknown nature, he gave this agency the name X-rays. He found that X-rays could manifest themselves by darkening wrapped photographic plates, discharging charged electroscopes, as well as by causing fluorescence in a number of different substances. He also found that X-rays can penetrate considerable thicknesses of materials of low atomic number, whereas substances of high atomic number are relatively opaque. Roentgen took the first steps in identifying the nature of X-rays by using a system of slits to show that (1) they travel in straight lines, and that (2) they are uncharged, because they are not deflected by electric or magnetic fields. Par. 3 The discovery of X-rays aroused the interest of all physicists, and many joined in the investigation of their properties. In 1899 Haga and Wind performed a single slit diffraction experiment with X-rays which showed that (3) X-rays are a wave motion phenomenon, and, from the size of the diffraction pattern, their wavelength could be estimated to be 10-8 cm. In 1906 Barkla proved that (4) the waves are transverse by showing that they can be polarized by scattering from many materials. Par. 4 There is, of course, no longer anything unknown about the nature of X-rays. They are electromagnetic radiation of exactly the same nature as visible light, except that their wavelength is several orders of magnitude shorter. This conclusion follows from comparing properties 1 through 4 with the similar properties of visible light, but it was actually postulated by Thomson several years before all these properties were known. Thomson argued that X-rays are electromagnetic radiation because such radiation would be expected to be emitted from the point at which the electrons strike the wall of a cathode ray tube. At this point, the electrons suffer very violent accelerations in coming to a stop and, according to classical electromagnetic theory, all accelerated charged particles emit electromagnetic radiations. We shall see later that this explanation of the production of X-rays is at least partially correct. Par. 5 In common with other electromagnetic radiations, X-rays exhibit particle-like aspects as well as wave-like aspects. The reader will recall that the Compton effect, which is one of the most convincing demonstrations of the existence of quanta, was originally observed with electromagnetic radiation in the X-ray region of wavelengths. When were X-rays discovered?

A、Par. 1

B、Par. 2

C、Par. 3

D、Par. 4

E、Par. 5

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第8题
Who discovered X-rays?

A、Par. 1

B、Par. 2

C、Par. 3

D、Par. 4

E、Par. 5

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第9题
What are the four characteristics of X-rays?

A、Par. 1

B、Par. 2

C、Par. 3

D、Par. 4

E、Par. 5

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