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.Prions and Illness
Prions are proteins responsible for several infectious diseases that can affect both humans and animals. In humans, prions cause a number of neurological diseases which result in a decrease in cognitive functions and that almost always end in death. Creutzfeldt-Jacob Disease—often called mad cow disease because of its debilitating effect on bovines—is one such prion disease that strikes the human brain. Some others are fatal familial insomnia, kuru, and Gerstmann-Straussler-Scheinker Disease (GSS).
These diseases, while different, share some similarities, particularly their cause. Prion proteins are attached to cell surfaces and are usually not harmful; however, in each of the aforementioned diseases, a prion protein in the brain assumes a wrong shape, disrupting the cell it is attached to. This signals nearby prion proteins to form improper shapes, too. The process slowly spreads across the brain as it destroys neurons, builds up plaque-like matter, and makes holes in brain tissue. It is slow moving, so it may take several years before the first symptoms are recognized.
There are three main forms of prion diseases: acquired, genetic, and sporadic. People get acquired prion diseases through infections by bad prions, typically through food. Kuru, a prion disease that was once common in New Guinea, was caused by cannibals eating the brains of people with bad prions, and Creutzfeldt-Jacob Disease, which humans get from ingesting infected beef, is another example. Genetic prion diseases are passed from parents to children through genes as an error causes the genes that code prion proteins to make mutant prion proteins that, as the children age, attach to cells in the wrong shapes. Fatal familial insomnia, which is found in a few families worldwide, causes people to be unable to sleep, and eventually leads to death, is one such example. As for sporadic prion diseases, they have no definitive causes. Experts believe they manifest because of mutant genes but are not certain why people acquire the diseases. Roughly 85% of prion diseases are sporadic as their victims are not exposed to infected food and have no family history of prion diseases.
*bovine: an animal such as a cow or buffalo
*neuron: a specialized cell that is a part of the nervous system
Prions are proteins responsible for several infectious diseases that can affect both humans and animals. In humans, prions cause a number of neurological diseases which result in a decrease in cognitive functions and that almost always end in death. Creutzfeldt-Jacob Disease—often called mad cow disease because of its debilitating effect on bovines—is one such prion disease that strikes the human brain. Some others are fatal familial insomnia, kuru, and Gerstmann-Straussler-Scheinker Disease (GSS).
These diseases, while different, share some similarities, particularly their cause. Prion proteins are attached to cell surfaces and are usually not harmful; however, in each of the aforementioned diseases, a prion protein in the brain assumes a wrong shape, disrupting the cell it is attached to. This signals nearby prion proteins to form improper shapes, too. The process slowly spreads across the brain as it destroys neurons, builds up plaque-like matter, and makes holes in brain tissue. It is slow moving, so it may take several years before the first symptoms are recognized.
There are three main forms of prion diseases: acquired, genetic, and sporadic. People get acquired prion diseases through infections by bad prions, typically through food. Kuru, a prion disease that was once common in New Guinea, was caused by cannibals eating the brains of people with bad prions, and Creutzfeldt-Jacob Disease, which humans get from ingesting infected beef, is another example. Genetic prion diseases are passed from parents to children through genes as an error causes the genes that code prion proteins to make mutant prion proteins that, as the children age, attach to cells in the wrong shapes. Fatal familial insomnia, which is found in a few families worldwide, causes people to be unable to sleep, and eventually leads to death, is one such example. As for sporadic prion diseases, they have no definitive causes. Experts believe they manifest because of mutant genes but are not certain why people acquire the diseases. Roughly 85% of prion diseases are sporadic as their victims are not exposed to infected food and have no family history of prion diseases.
*bovine: an animal such as a cow or buffalo
*neuron: a specialized cell that is a part of the nervous system
填空题
3. An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas of the passage. Some sentences do not belong because they express ideas that are not presented in the passage or are minor ideas in the passage.
Prions are proteins that can cause various types of diseases to infect the brains of their victims.
ANSWER CHOICES
①Sporadic prion diseases are not caused by infected food or genetics, so their causes are a complete mystery.
②Medical researchers believe that they can cure some of the best-known prion diseases, including Creutzfeldt-Jacob Disease.
③Sporadic prion diseases are the most common, but there are also acquired and genetic prion diseases.
④When prions take the wrong shape, they cause other prions to do the same thing, and this can spread through the brain.
⑤When a person is infected by a prion disease, that individual's thinking processes are weakened, and the disease is nearly always fatal.
⑥Only a few families around the world are affected by the genetic prion disease that is called fatal familial insomnia.
Prions are proteins that can cause various types of diseases to infect the brains of their victims.
ANSWER CHOICES
①Sporadic prion diseases are not caused by infected food or genetics, so their causes are a complete mystery.
②Medical researchers believe that they can cure some of the best-known prion diseases, including Creutzfeldt-Jacob Disease.
③Sporadic prion diseases are the most common, but there are also acquired and genetic prion diseases.
④When prions take the wrong shape, they cause other prions to do the same thing, and this can spread through the brain.
⑤When a person is infected by a prion disease, that individual's thinking processes are weakened, and the disease is nearly always fatal.
⑥Only a few families around the world are affected by the genetic prion disease that is called fatal familial insomnia.
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4. Mapping
The following chart shows the structure of the passage. Fill in the blanks with the appropriate words.
The following chart shows the structure of the passage. Fill in the blanks with the appropriate words.
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5. Summary
The following is a summary of the passage. Fill in the blanks with the appropriate words.
Prions are 5 that can cause various diseases in both humans and animals. The diseases they cause in humans, such as Creutzfeldt-Jacobs Disease, fatal familial insomnia, kuru, and Gerstmann-Straussler-Scheinker Disease, almost always 6 the infected people. What happens is that a prion protein in the brain assumes the wrong 7 , and then it causes nearby prion proteins to do the same thing. This spreads across the brain, destroys neurons, builds up plaque-like matter, and creates 8 in brain tissue. Prion diseases can be acquired, genetic, or sporadic. 9 prion diseases are typically gotten from food. 10 prion diseases are passed from parents to children, and 11 prion diseases have no known causes.
The following is a summary of the passage. Fill in the blanks with the appropriate words.
Prions are 5 that can cause various diseases in both humans and animals. The diseases they cause in humans, such as Creutzfeldt-Jacobs Disease, fatal familial insomnia, kuru, and Gerstmann-Straussler-Scheinker Disease, almost always 6 the infected people. What happens is that a prion protein in the brain assumes the wrong 7 , and then it causes nearby prion proteins to do the same thing. This spreads across the brain, destroys neurons, builds up plaque-like matter, and creates 8 in brain tissue. Prion diseases can be acquired, genetic, or sporadic. 9 prion diseases are typically gotten from food. 10 prion diseases are passed from parents to children, and 11 prion diseases have no known causes.
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