Do you agree with the strategy of xenotransplantation to alleviate the shortage of donated human organs? Why or
why not? What will be an ideal response?
ANSWER: Answers will vary.
Background:In
the United States, almost 29,000 organs were transplanted in 2013, but about 77,000
qualified patients are on waiting lists. Each year, almost 4,000 people on waiting lists die
before receiving transplants, and another 100,000 die even before they are placed on a
waiting list. Although the demand for organ transplants is rising, the number of donated
organs is growing very slowly. As outlined at the beginning of this chapter, one way to
increase the supply of organs is to use animal donors for transplants. Animal–human
transplants (called xenotransplants) have been attempted many times, but with little success.
Two important biological problems are related to xenotransplants: (1) complement-mediated
rejection and (2) T cell–mediated rejection.
Proponents of xenotransplantation point to the lives that will be saved if pig organs can be
used for organ transplants. Opponents point out that there is no evidence that pig organs will
work properly in humans and that pig organs may harbor harmful viruses that will be
transferred to the human recipients. Others question the ethics of genetically modifying
animals with human genes or modifying humans by transplanting parts of the pig’s immune
system.
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Upon chemical analysis, a particular polypeptide was found to contain 100 amino acids. How many peptide bonds are present in this protein?
A) 101 B) 100 C) 99 D) 98 E) 97
Answer the following statements true (T) or false (F)
1. The same hormone can cause vasoconstriction in some arterioles and vasodilation in others. 2. Cardiac output depends solely on the heart rate. 3. Rises in blood pressure with large increases in cardiac output are limited by decreases in total peripheral resistance. 4. A reduction in blood pressure due to hemorrhage would be expected to increase stimulation of baroreceptors.
The enzyme used by retroviruses to make a DNA copy of their RNA genome is called
A. RNA polymerase. B. reverse transcriptase. C. DNA polymerase. D. RNA replicase.
Which of the following is incorrect regarding the complement fixation test?
A.) first antigen and antibody are allowed to react B.) purified complement proteins are added to the antigen-antibody tube C.) sheep red blood cells are added to the antigen -antibody-complement mixture D.) hemolysis of the sheep red blood cells occurs in a positive test result