The new miracle of the medical world is the stem cell, a marvel of human nature in that it can become any of nearly 220 cell types that constitute the human body. It is often called a blank cell that can be programmed to become other cells. Researchers predict that, by using stem cells, they can create organs that can be transplanted into people who desperately need them to save their lives. The most common source of stem cells is the human embryo, the initial stage of human life after a female egg is impregnated by a male sperm. In this very fact lies an ethical conundrum that has rocked both the medical and political landscape of the United States and other countries. Coupled with this is new research in cloning, which has seen some success in developing animal species without the use of normal birthing procedures. All of these areas of research are making quite a few people nervous about both the sources of stem cells and where the research is taking mankind.
Most stem cell-containing embryos come from four different sources: fertility clinics, which often store more human embryos than are needed; fetuses from unwanted pregnancies that are aborted; therapeutic cloning, which is when a human egg is stimulated into an embryo-like state; and custom-fertilization, in which a human egg is deliberately fertilized with sperm to create an embryo in order to harvest its stem cells. Morally, many people are outraged by these sources, claiming that human life is not something that should be tampered with and created just for scientific and medical purposes. At the core of this debate is the issue of what really constitutes a human being, with one side claiming a human does not exist until born rom its mother while the other side claims that once egg and sperm meet, life has begun.
The United States government has taken an active role in the debate and is consciously looking at the voting booth while making decisions regarding stem cell research. The government gave the go-ahead for federal spending on stem cell research but limited activity to specimens that already existed, meaning no new embryos could be created solely for stem cell research. Similar laws regarding cloning research have been proposed, including therapeutic cloning. Many universities and research centers worry that these laws may cause their best and brightest scientists to seek appointments overseas, where stem cell research is not so controversial.
Scientists now seek non-embryonic sources of stem cells to avoid the controversy in the future and to allow them to carry out their work without interference. Unfortunately, so far the search has not unearthed any sources that are as perfect as human embryo stem cells. The main reason they are not perfect is that, while embryo stem cells can become any other cell, other stem cells from different sources can only become limited types of cells. Research suggests that inside each person there is a limited supply of stem cells in the blood that are used to repair red blood cells when they are damaged. Some scientists believe they may be able to harvest these cells, but results so far have had limited success in extracting and using them to produce other cells. Even the limited successes they have had are being questioned by other experts as unproven. Two other sources, baby teeth and adult bone marrow, show some possibilities, but again the research is being questioned, and, as of yet, no positive new source of stem cells has been found to replace human embryos.
In view of the ethical debate that surrounds stem cell research, especially its sources of stem cells, it is likely that it will be some time before the whole issue is laid to rest. Meanwhile, countless people suffer from illnesses that could be cured or their pain alleviated by the work that comes from stem cell research. Some people believe that the debate about when human life actually begins needs to take a backseat to the issue of when human life will end, especially when it is possible to save someone from an early death. In the end, the research will likely get done in a place that puts existing human life above that in the embryonic state. It is also highly unlikely that that place will be the United States.
1. According to paragraph 1, a stem cell is unlike other cells because（ ）.
2. According to paragraph 2, the main debate concerning stem cell sources revolves around（ ）.
3. According to paragraph 3, American universities and research institutes are worried about（ ）.
4. Which of the sentences below best expresses the essential information in paragraph 3. Incorrect answer choices change the meaning in important ways or leave out essential information.
5. It can be inferred from paragraph 5 that in many countries stem cell research（ ）.
