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Once a rarely used subset of medical treatments, protein therapeutics have increased dramatically in number and frequency of use since the introduction of the first recombinant protein therapeutic–human insulin–25 years ago. Protein therapeutics already have a significant role in almost every field of medicine, but this role is still only in its infancy. Human proteins, such as erythropoietin, granulocyte colony–stimulating factor and alpha-L-iduronidase, are in great demand for the treatment of a variety of diseases. Whereas some can be purified from blood, this is expensive and runs the risk of contamination by AIDS or hepatitis C. Proteins can be produced in human cell culture but costs are very high and output small. Much larger quantities can be produced in bacteria or yeast but the proteins produced can be difficult to purify and they lack the appropriate post-translational modifications that are needed for efficacy in vivo.
By contrast, human proteins that have appropriate post-translational modifications can be produced in the milk of transgenic sheep, goats and cattle. Currently, research groups around the world are investigating whether transgenic animals such as goats, cattle, pigs, rabbits and chickens can be used to produce therapeutic proteins. The animals are used as sterile bioreactors to produce large, complex proteins or proteins that can’t be made in other cell systems. Output can be as high as 40 g per liter of milk and costs are relatively low. An advantage of producing transgenic animals is it uses less than half the experimental animals than does pronuclear injection. Also, it is possible to specify the sex of offspring and thereby reduce the time taken to generate a flock. The main disadvantages of making therapeutic proteins in animals are that it takes a long time to generate and validate transgenic animals, that proteins can’t be harvested until lactation begins, and that the transgene may affect the animal, for example, as the transgene inserts randomly into a chromosome, it may disrupt a gene required for an important function. Notwithstanding these, the number of therapeutic proteins being developed by the biomedical industry is growing rapidly, and some scientists are predicting that demand for proteins will soon exceed their ability to supply them. Transgenic animals could provide an alternative source of therapeutic proteins to help meet these demands.
1. Which of the following would best serve as an appropriate title for the given passage?
(A) Transgenic animals and proteins
(B) Human proteins from transgenic animals
(C) Human protein harvesting
(D) Protein therapeutics
(E) Advantages and disadvantages of protein therapeutics
2. According to the passage, what is one of the advantages of human proteins over proteins obtained from bacteria?
(A) They can be produced in much larger quantities.
(B) They can be produced in exceedingly pure forms.
(C) They can be produced at much higher costs than any other.
(D) They take the least amount of time to produce.
(E) They can be given the appropriate post-translational modifications.
3. Which of the following questions does the passage answer?
(A) Why is the output of proteins from human cell cultures limited?
(B) Why are the proteins produced from bacteria unsuitable for use in treatments?
(C) How much usable protein is produced by a flock of transgenic animals?
(D) Why are animals better for transgenic production than sheep?
(E) What diseases can be cured from protein therapeutics and not by any other method?
4. According to the passage, all of the following is unsupported about protein therapeutics, EXCEPT that they
(A) can be used to treat AIDS and Hepatitis C.
(B) cure diabetes in humans.
(C) cannot be produced in transgenic animals.
(D) are used to create human insulin.
(E) treat undefined conditions.
5. According to the passage, which of the following can be said about animals produced by pronuclear injection?
(A) It takes twice the time to produce a pronuclear flock.
(B) It isn’t possible to predict their sex.
(C) More than double the number of transgenic animals is required to produce the same quantity of tissue activators.
(D) They make better test animals than do transgenic animals.
(E) Most animals cannot be produced with pronuclear injection but sheep can.
6. According to the passage, with which of the following statements would the author most likely agree?
(A) Producing human proteins in transgenic animals can be an alternative source of treatment.
(B) Human proteins are the best possible way for future research in medicine.
(C) Human proteins from transgenic animals is the only way we can meet the demands of the medical industry.
(D) Harvesting human proteins from bacteria or blood is absolutely unnecessary and economically unfeasible.
(E) Protein therapeutics is the most important discovery of the previous century in medical research.
7. Which of the following, if true, would most weaken the author’s contention against proteins produced from human cell culture?
(A) Proteins from human cell culture are the purest possible forms.
(B) The bigger the output required, the lower the cost of human cell culturing.
(C) Human cell culture is not opposed, as is producing transgenic animals, by animal rights activists.
(D) Culturing human cells in a lab is possible with a minimum amount of equipment and takes half the time of producing transgenic animals.
(E) Proteins produced in human cell culture are devoid of contamination and very accurate in replication.
参考答案： CEBDBAB
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发表于 2021-7-7 05:35:49
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