Passage 36
Protein synthesis begins when the gene encoding a protein is activated. The gene’s sequence of nucleotides is transcribed into a molecule of messenger RNA (mRNA), which reproduces the information contained in that(5) sequence. Transported outside the nucleus to the cytoplasm, the mRNA is translated into the protein it encodes by an organelle known as a ribosome, which strings together amino acids in the order specified by the sequence of elements in the mRNA molecule. Since the(10) amount of mRNA in a cell determines the amount of the corresponding protein, factors affecting the abundance of mRNA’s play a major part in the normal functioning of a cell by appropriately regulating protein synthesis. For example, an excess of certain proteins can cause cells(15)to proliferate abnormally and become cancerous; a lack of the protein insulin results in diabetes.
Biologists once assumed that the variable rates at which cells synthesize different mRNA’s determine the quantities of mRNA’s and their corresponding proteins(20) in a cell. However, recent investigations have shown that the concentrations of most mRNA’s correlate best, not with their synthesis rate, but rather with the equally variable rates at which cells degrade the different mRNA’s in their cytoplasm. If a cell degrades both a rapidly and(25) a slowly synthesized mRNA slowly, both mRNA’s will accumulate to high levels.
An important example of this phenomenon is the development of red blood cells from their unspecialized parent cells in bone marrow. For red blood cells to accu(30) mulate sufficient concentrations of hemoglobin (which transports oxygen) to carry out their main function, the cells’ parent cells must simultaneously produce more of the constituent proteins of hemoglobin and less of most other proteins. To do this, the parent cells halt synthesis(35) of no hemoglobin mRNA’s in the nucleus and rapidly degrade copies of the no hemoglobin mRNA’sremaining in the cytoplasm. Halting synthesis of mRNA alone would not affect the quantities of proteins synthesized by the mRNA’s still existing in the cytoplasm. Biologists now(40) believe that most cells can regulate protein production most efficiently by varying both mRNA synthesis and degradation, as developing red cells do, rather than by just varying one or the other.
1. The passage is primarily concerned with discussing the
(A) influence of mRNA concentrations on the development of red blood cells
(B) role of the synthesis and degradation of mRNA in cell functioning
(C) mechanism by which genes are transcribed into mRNA
(D) differences in mRNA concentrations in cell nuclei and in the cytoplasm
(E) way in which mRNA synthesis contributes to the onset of diabetes
2. The passage suggests that a biologist who held the view described in the first sentence of the second paragraph would most probably also have believed which of the following?
(A) The rate of degradation of specific mRNA’s has little effect on protein concentrations.
(B) The rate of degradation of specific mRNA’s should be studied intensively.
(C) The rates of synthesis and degradation for any given mRNA are normally equal.
(D) Different mRNA’s undergo degradation at widely varying rates.
(E) Most mRNA’s degrade very rpaidly.
3. Which of the following best describes the relationship between the second and third paragraphs of the passage?
(A) The second paragraph presents arguments in support of a new theory and the third paragraph presents arguments against that same theory.
(B) The second paragraph describes a traditional view and the third paragraph describes the view that has replaced it on the basis of recent investigations.
(C) The third paragraph describes a specific case of a phenomenon that is described generally in the second paragraph.
(D) The third paragraph describes an investigation that was undertaken to resolve problems raised by phenomena described in the second paragraph.
(E) Both paragraphs describe in detail specific examples of the phenomenon that is introduced in the first paragraph.
4. The accumulation of concentrations of hemoglobin in red blood cells is mentioned in the passage as an example of which of the following?
(A) The effectiveness of simultaneous variation of the rates of synthesis and degradation of mRNA
(B) The role of the ribosome in enabling a parent cell to develop properly into a more specialized form
(C) The importance of activating the genes for particular proteins at the correct moment
(D) The abnormal proliferation of a protein that threatens to make the cell cancerous
(E) The kind of evidence that biologists relied on for support of a view of mRNA synthesis that is now considered obsolete
5. To begin to control a disease caused by a protein deficiency, the passage suggests that a promising experimental treatment would be to administer a drug that would reduce
(A) only the degradation rate for the mRNA of the protein involved
(B) only the synthesis rate for the mRNA of the protein involved
(C) both the synthesis and degradation rates for the mRNA of the protein involved
(D) the incidence of errors in the transcription of mRNA’s from genetic nucleotide sequences
(E) the rate of activity of ribosomes in the cytoplasm of most cells
6. According to the passage, which of the following best describes the current view on the relationship between the synthesis and the degradation of mRNA in regulating protein synthesis?
(A) Biologists have recently become convinced that the ribosome controls the rates of synthesis and degradation of mRNA.
(B) There is no consensus among biologists as to the significance of mRNA degradation in regulating protein synthesis.
(C) The concept of mRNA degradation is so new that most biologists still believe that the vital role in protein regulation belongs to mRNA synthesis.
(D) Degradation of mRNA is now considered to be the key process and mRNA synthesis is no longer believed to play a significant role.
(E) Degradation of mRNA is now considered to be as important as mRNA synthesis has been, and still is, believed to be.
7. According to the passage, which of the following can happen when protein synthesis is not appropriately regulated?
(A) Diabetes can result from errors that occur when the ribosomes translate mRNA into protein.
(B) Cancer can result from an excess of certain proteins and diabetes can result from an insulin deficiency.
(C) A deficiency of red blood cells can occur if bone marrow cells produce too much hemoglobin.
(D) Cancer can be caused by excessively rapid degradation of certain amino acids in the cytoplasm of cells.
(E) Excessive synthesis of one protein can trigger increased degradation of mRNA’s for other proteins and create severe protein imbalances.
8. The passage suggests that a biologist who detected high levels of two proteins in a certain type of cell would be likely to consider which of the following as a possible explanation?
(A) The rate of mRNA degradation for one of the proteins increases as this type of cell develops a more specialized function.
(B) The two proteins are most likely constituents of a complex substance supporting the cells’ specialized function.
(C) The cells are likely to proliferate abnormally and possibly become cancerous due to the levels of these proteins.
(D) The mRNA’s for both proteins are being degraded at a low rate in that type of cell.
(E) The mRNA’s for the two proteins are being synthesized at identical rates in that type of cell.
Passage 37
Japanese firms have achieved the highest levels of manufacturing efficiency in the world automobile industry. Some observers of Japan have assumed that Japanese firms use the same manufacturing equipment(5) and techniques as United States firms but have benefited from the unique characteristics of Japanese employees and the Japanese culture. However, if this were true, then one would expect Japanese auto plants in the United States to perform no better than factories(10) run by United States companies. This is not the case, Japanese-run automobile plants located in the United States and staffed by local workers have demonstrated higher levels of productivity when compared with factories owned by United States companies.(15)Other observers link high Japanese productivity to higher levels of capital investment per worker. But a historical perspective leads to a different conclusion. When the two top Japanese automobile makers matched and then doubled United States productivity(20) levels in the mid-sixties, capital investment per employee was comparable to that of United States firms. Furthermore, by the late seventies, the amount of fixed assets required to produce one vehicle was roughly equivalent in Japan and in the United States.(25) Since capital investment was not higher in Japan, it had to be other factors that led to higher productivity.
A more fruitful explanation may lie with Japanese production techniques. Japanese automobile producers did not simply implement conventional processes more(30) effectively: they made critical changes in United States procedures. For instance, the mass-production philosophy of United States automakers encouraged the production of huge lots of cars in order to utilize fully expensive, component-specific equipment and to(35) occupy fully workers who have been trained to execute one operation efficiently. Japanese automakers chose to make small-lot production feasible by introducing several departures from United States practices, including the use of flexible equipment that could be(40) altered easily to do several different production tasks and the training of workers in multiple jobs.
Automakers could schedule the production of different components or models on single machines, thereby eliminating the need to store the buffer stocks of extra(45) components that result when specialized equipment and workers are kept constantly active.
1. The primary purpose of the passage is to
(A) present the major steps of a process
(B) clarify an ambiguity
(C) chronicle a dispute
(D) correct misconceptions
(E) defend an accepted approach
2. The author suggests that if the observers of Japan mentioned in line 3 were correct, which of the following would be the case?
(A) The equipment used in Japanese automobile plants would be different from the equipment used in United States plants.
(B) Japanese workers would be trained to do several different production jobs.
(C) Culture would not have an influence on the productivity levels of workers.
(D) The workers in Japanese-run plants would have higher productivity levels regardless of where they were located.
(E) The production levels of Japanese-run plants located in the United States would be equal to those of plants run by United States companies.
3. Which of the following statements concerning the productivity levels of automakers can be inferred from the passage?
(A) Prior to the 1960’s, the productivity levels of the top Japanese automakers were exceeded by those of United States automakers.
(B) The culture of a country has a large effect on the productivity levels of its automakers.
(C) During the late 1970’s and early 1980’s,productivity levels were comparable in Japan and the United States.
(D) The
greater the number of cars that are produced in a single lot, the higher a plant’s productivity level.
(E) The amount of capital investment made by automobile manufacturers in their factories determines the level of productivity.
4. According to the passage, which of the following statements is true of Japanese automobile workers?
(A) Their productivity levels did not equal those of United States automobile workers until the late seventies.
(B) Their high efficiency levels are a direct result of cultural influences.
(C) They operate component-specific machinery.
(D) They are trained to do more than one job.
(E) They produce larger lots of cars than do workers in United States factories.
5. Which of the following best describes the organization of the first paragraph?
(A) A thesis is presented and supporting examples are provided.
(B) Opposing views are presented, classified, and then reconciled.
(C) A fact is stated, and an explanation is advanced and then refuted.
(D) A theory is proposed, considered, and then amended.
(E) An opinion is presented, qualified, and then reaffirmed.
6. It can be inferred from the passage that one problem associated with the production of huge lots of cars is which of the following?
(A) The need to manufacture flexible machinery and equipment
(B) The need to store extra components not required for immediate use
(C) The need for expensive training programs for workers, which emphasize the development of facility in several production jobs.
(D) The need to alter conventional mass-production processes
(E) The need to increase the investment per vehicle in order to achieve high productivity levels
7. Which of the following statements is supported by information stated in the passage?
(A) Japanese and United States automakers differ in their approach to production processes.
(B) Japanese automakers have perfected the use of single-function equipment.
(C) Japanese automakers invest more capital per employee than do United States automakers.
(D) United States-owned factories abroad have higher production levels than do Japanese owned plants in the United States.
(E) Japanese automakers have benefited from the cultural heritage of their workers.
8. With which of the following predictive statement regarding Japanese automakers would the author most likely agree?
(A) The efficiency levels of the Japanese automakers will decline if they become less flexible in their approach to production
(B) Japanese automakers productivity levels double during the late 1990’s.
(C) United States automakes will originate net production processes before Japanese automakers do.
(D) Japanese automakers will hire fewer workers than will United States automakers because each worker is required to perform several jobs.
(E) Japanese automakers will spend less on equipment repairs than will United States automakers because apanese equipment can be easily altered.
Passage 38
It was once believed that the brain was independent of metabolic processes occurring elsewhere in the body.In recent studies, however, we have discovered that the production and release in brain neurons of the neuro(5) transmitter serotonin (neurotransmitters are compounds that neurons use to transmit signals to other cells) depend directly on the food that the body processes.
Our first studies sought to determine whether the increase in serotonin observed in rats given a large injec(10)tion of the amino acid tryptophan might also occur after rats ate meals that change tryptophan levels in the blood. We found that, immediately after the rats began to eat, parallel elevations occurred in blood tryptophan, brain tryptophan, and brain serotonin levels. These find-(15) ings suggested that the production and release of serotonin in brain neurons were normally coupled with blood-tryptophan increases. In later studies we found that injecting insulin into a rat’s bloodstream also caused parallel elevations in blood and brain tryptophan levels(20) and in serotonin levels. We then decided to see whether the secretion of the animal’s own insulin similarly affected serotonin production. We gave the rats a carbohydrate- containing meal that we knew would elicit insulin secretion. As we had hypothesized, the blood tryptophan (25) level and the concentrations of tryptophan serotonin in the brain increased after the meal.
Surprisingly, however, when we added a large amount of protein to the meal, brain tryptophan and serotonin levels fell. Since protein contains tryptophan,(30)why should it depress brain tryptophan levels? The answer lies in the mechanism that provides blood tryptophan to the brain cells. This same mechanism also provides the brain cells with other amino acids found in protein, such as tyrosine and leucine. The consumption(35) of protein increases blood concentration of the other amino acids much more, proportionately, than it does that of tryptophan. The more protein in the meal, the lower is the ratio of the resulting blood-tryptophan concentration to the concentration of competing amino(40) acids, and the more slowly is tryptophan provided to the brain. Thus the more protein in a meal, the less serotonin subsequently produced and released.
1. Which of the following titles best summarizes the contents of the passage?
(A) Neurotransmitters: Their Crucial Function in Cellular Communication
(B) Diet and Survival: An Old Relationship Reexamined
(C) The Blood Supply and the Brain: A Reciprocal Dependence
(D) Amino Acids and Neurotransmitters: The Connection Between Serotonin Levels and Tyrosine
(E) The Effects of Food Intake on the Production and Release of Serotonin: Some Recent Findings
2. According to the passage, the speed with which tryptophan is provided to the brain cells of a rat varies with the
(A) amount of protein present in a meal
(B) concentration of serotonin in the brain before a meal
(C) concentration of leucine in the blood rather than on the concentration of tyrosine in the blood after a meal
(D) concentration of tryptophan in the brain before a meal
(E) number of serotonin-containing neurons present in the brain before a meal
3. According to the passage, when the authors began their first studies, they were aware that
(A) they would eventually need to design experiments that involved feeding rats high concentrations of protein
(B) tryptophan levels in the blood were difficult to monitor with accuracy
(C) serotonin levels increased after rats were fed meals rich in tryptophan
(D) there were many neurotransmitters whose production was dependent on metabolic processes elsewhere in the body.
(E) serotonin levels increased after rats were injected with a large amount of tryptophan
4. According to the passage, one reason that the authors gave rats carbohydrates was to
(A) depress the rats’ tryptophan levels
(B) prevent the rats from contracting diseases
(C) cause the rats to produce insulin
(D) demonstrate that insulin is the most important substance secreted by the body
(E) compare the effect of carbohydrates with the effect of proteins
5. According to the passage, the more protein a rat consumes, the lower will be the
(A) ratio of the rat’s blood-tryptophan concentration to the amount of serotonin produced and released in the rat’s brain
(B) ratio of the rat’s blood-tryptophan concentration to the concentration in its blood of the other amino acids contained in the protein
(C) ratio of the rat’s blood-tyrosine concentration to its blood-leucine concentration
(D) number of neurotransmitters of any kind that the rat will produce and release
(E) number of amino acids the rat’s blood will contain
6. The authors’ discussion of the “mechanism that provides blood tryptophan to the brain cells” (lines 31-32) is meant to
(A) stimulate further research studies
(B) summarize an area of scientific investigation
(C) help explain why a particular research finding was obtained
(D) provide supporting evidence for a controversial scientific theory
(E) refute the conclusions of a previously mentioned research study
7. According to the passage, an injection of insulin was most similar in its effect on rats to an injection of
(A) tyrosine
(B) leucine
(C) blood
(D) tryptophan
(E) protein
8. It can be inferred from the passage that which of the following would be LEAST likely to be a potential source of aid to a patient who was not adequately producing and releasing serotonin?
(A) Meals consisting almost exclusively of protein
(B) Meals consisting almost exclusively of carbohydrates
(C) Meals that would elicit insulin secretion
(D) Meals that had very low concentrations of tyrosine
(E) Meals that had very low concentrations of leucine
9. It can be inferred from the passage that the authors initially held which of the following hypotheses about what would happen when they fed large amounts of protein to rats?
(A) The rats’ brain serotonin levels would not decrease.
(B) The rats’ brain tryptophan levels would decrease
(C) The rats’ tyrosine levels would increase less quickly than would their leucine levels
(D) The rats would produce more insulin.
(E) The rats would produce neurotransmitters other than serotonin.
Passage 39
Historians sometimes forget that history is communally being made and experienced before it is studied,interpreted, and read. These latter activities have their own history, of course, which may impinge in unex-(5) pected ways on public events. It is difficult to predict when “new pasts” will overturn established historical interpretations and change the course of history.
In the fall of 1954, for example, C. Vann Woodward delivered a lecture series at the University of Virginia (10) which challenged the prevailling dogma concerning the history, continuity, and uniformity of racial segregation in the South. He argued that the Jim Crow laws of the late nineteenth and early twentieth centuries not only codified traditional practice but also were a determined(15) effort to erase the considerable progress made by Black people during and after Reconstruction in the 1870’s.
This revisionist view of Jim Crow legislation grew in Part from the research that Woodward had done for the NAACP legal campaign during its preparation for(20)Brown v. Board of Education. The Supreme Court had issued its ruling in this epochal desegregation case a few months before Woodward’s lectures.
The lectures were soon published as a book. The Strange Career of Jim Crow. Ten years later, in a (25)preface to the second revised edition. Woodward confessed with ironic modesty that the first edition “had begun to suffer under some of the handicaps that might be expected in a history of the American Revolution published in 1776.” That was a bit like hearing(30)Thomas Paine apologize for the timing of his pamphlet Common Sense, which had a comparable impact.
Although Common Sense also had a mass readership. Paine had intended to reach and inspire: he was not a historian, and thus not concerned with accuracy or the(35) dangers of historical anachronism. Yet, like Paine,Woodward had an unerring sense of the revolutionary moment, and of how historical evidence could undermine the mythological tradition that was crushing the dreams of new social possibilities. Martin Luther King,(40) Jr.. testified to the profound effect of The StrangeCareer of Jim Crow on the civil rights movement by praising the book and quoting it frequently.
1. The “new pasts” mentioned in line 6 can best be described as the
(A) occurrence of events extremely similar to past events
(B) history of the activities of studying, interpreting, and reading new historical writing
(C) change in people’s understanding of the past due to more recent historical writing
(D) overturning of established historical interpretations by politically motivated politicians
(E) difficulty of predicting when a given historical interpretation will be overturned
2. It can be inferred from the passage that the “prevailling dogma” (line 10) held that
(A) Jim Crow laws were passed to give legal status to well-established discriminatory practices in the South
(B) Jim Crow laws were passed to establish order and uniformity in the discriminatory practices of different southern states.
(C) Jim Crow laws were passed to erase the social gains that Black people had achieved since Reconstruction
(D) the continuity of racial segregation in the South was disrupted by passage of Jim Crow laws
(E) the Jim Crow laws of the late nineteenth and early twentieth centuries were passed to reverse the effect of earlier Jim Crow laws
3. Which of the following is the best example of writing that is likely to be subject to the kinds of “handicaps” referred to in line 27?
(A) A history of an auto manufacturing plant written by an employee during an autobuying boom
(B) A critique of a statewide school-desegregation plan written by an elementary school teacher in that state
(C) A newspaper article assessing the historical importance of a United States President written shortly after the President has taken office
(D) A scientific paper describing the benefits of a certain surgical technique written by the surgeon who developed the technique
(E) Diary entries narrating the events of a battle written by a soldier who participated in the battle
4. The passage suggests that C. Vann Woodward and Thomas Paine were similar in all of the following ways EXCEPT:
(A) Both had works published in the midst of important historical events.
(B) Both wrote works that enjoyed widespread popularity.
(C) Both exhibited an understanding of the relevance of historical evidence to contemporary issues.
(D) The works of both had a significant effect on events following their publication.
(E) Both were able to set aside worries about historical anachronism in order to reach and inspire.
5. The attitude of the author of the passage toward the work of C. Vann Woodward is best described as one of
(A) respectful regard
(B) qualified approbation
(C) implied skepticism
(D) pointed criticism
(E) fervent advocacy
6. Which of the following best describes the new idea expressed by C. Vann Woodward in his University of Virginia lectures in 1954?
(A) Southern racial segregation was continuous and uniform.
(B) Black people made considerable progress only after Reconstruction.
(C) Jim Crow legislation was conventional in nature.
(D) Jim Crow laws did not go as far in codifying traditional practice as they might have.
(E) Jim Crow laws did much more than merely reinforce a tradition of segregation.
