The Passage
As you read the passage, you'll be allowed to take notes on your scrap paper.
(1) Stem cells are effectively blank slates that can differentiate into other types of cells, an ability that makes them useful for scientists researching treatments for many different kinds of diseases and injuries. (2) However, their utility has not protected them from controversy. (3) Some stem cells can be taken from the blood, bone marrow, and fat tissue of adults, but adult stem cells have a limited ability to differentiate. (4) The most versatile and useful stem cells for research and medical use come from human embryos. (5) To use the stem cells for research, scientists have to destroy the embryos, which qualifies as murder according to people who believe that human life begins at the moment of conception. (6)This has sparked an intense debate between opponents of embryonic destruction and the scientists who disagree with their definition of human life and need embryonic stem cells for applications where adult stem cells are not viable.
The Questions
That was the passage; now, it's time for the questions.
1. Which of the following does the passage identify as a reason why the stem cell controversy cannot simply be solved by using only adult stem cells?
- The use of stem cells from adult blood, bone marrow, and fat tissue
- The use of cells that can differentiate into other types of cells
- The greater utility of embryonic stem cells, compared to adult cells
- The objections of people who believe that life begins at conception
- The use of cells from human umbilical cords
Go back to the passage if you like and find an answer based on the text.
Ready to hear the answer? The correct answer is C. In sentence three, the author mentions adult cells' 'limited ability to differentiate', and sentence six discusses 'applications where adult stem cells are not viable'. In other words, embryonic stem cells are needed for some applications where adult stem cells just won't do the job.
Watch for trap answers, like E - choice E sounds familiar if you know outside information about stem cells, but the passage doesn't mention umbilical cords anywhere!
Ready for the next question?
2. Which of the following arguments would provide a way of sidestepping the controversy that the author raises in this article? This question may have multiple correct answers; select all that apply.
- Some researchers have developed a technique for extracting stem cells from an embryo without destroying it
- Researchers are close to discovering a way to change adult stem cells so that they differentiate as well as embryonic cells
- When being treated with stem cells, the patient's immune system sometimes accepts his or her own stem cells, but rejects embryonic cells
Again, if you want the passage back, just go to the beginning of THE PASSAGE section.
The correct answers are A and B. Choice A would sidestep the controversy because the objections raised in the passage hinge on the fact that the embryo is destroyed. If the embryo is not destroyed, there would be no reason to object. Choice B would sidestep the controversy by eliminating the need for embryonic stem cells at all, while still giving the researchers everything they need.
Choice C is an argument in favor of using adult stem cells for certain applications, but it does not address the main controversy in the passage, so it isn't a correct answer.
3. Select the sentence that characterizes opponents of embryonic stem cell research.
You'll notice in the passage that the sentences are numbered one through six to make it easy for you. Pick the number of the correct sentence.
The correct answer is (5). This sentence characterizes the opponents as 'people who believe that human life begins at the moment of conception.'