of Contents | Glossary
Mrs. Fister Can Replace
||A sperm fertilizes an egg cell to begin the process of sexual reproduction.|
When a male's sperm fertilizes a female egg, it creates a single cell in which an equal number of chromosomes from the male and the female parents are united. The fertilized egg soon divides into two connected cells. Each of these two cells carries a complete copy of the chromosomes that were in the original cell. These two cells then divide again. This process keeps repeating to form a many-celled embryo.
After the first few rounds of divisions, cells begin to specialize. For example, some cells become nerve cells, some become skin cells, and some become blood cells. In each kind, different genes come into play. The genetic instructions that go into operation in each cell dictate the production of the particular proteins that make up the cell's structure and direct its activities.
||A fertilized egg cell divides into two connected cells. The cells continue to divide, but each new cell contains a complete copy of the chromosomes in the original cell.|
The removed cells were cultivated, or kept alive, in a laboratory dish. Then the researchers reduced the nourishment they had been giving these cells. The cells went into a resting state, like a coma. This was the key step. In the resting state, the specific genetic instructions in operation in the cells were erased. Each cell contained a full set of genes, but no specific genes were turned on. In other words, they were now prepared to divide into cells that could specialize anew, into any kind of cell.
||These specialized cells are from a rabbit liver|
This egg was cultivated until it had grown into a several-celled embryo. Then it was implanted in the uterus of a third sheep, a surrogate,who carried the lamp until she was born and became known to the world as Dolly.
To produce the rhesus monkeys, a similar method was used. However, the researchers obtained their genetic material for cloning from the cells of early-stage embryos. These cells were not fully differentiated like the mature cells that had been used to produce Dolly. In other words, these cells did not need to be prodded back into a resting state before their nuclei could be transferred into nucleus-free eggs. (The two monkeys each developed from the cell of a different embryo. Therefore they are not genetically identical to each other.)
"Cloning" is the shorthand way of referring to the procedure described above. However, there are lots of ways to clone, or make copies of things, so the specific name for this producer is nuclear transfer technology. The key importance of nuclear transfer technology. is that a whole set of chromosomes is lifted from one already-existing animal to create a genetically identical animal. Dolly does not carry a combination of genes contributed by a mother and father. Rather, she is the genetic equal of the sheep that donated a nucleus.
Nuclear transfer technology is not new. Scientists have been experimenting with it for years. They have used it to produce cows and sheep from embryo cells. They have used it to grow frogs, as far as the tadpole state, from mature cells. What is new with the Dolly experiment is that researchers have figured out how to successfully set embryo development in motion once they have transplanted the genetic material from a mature cell into an egg. And the significance of the rhesus monkey experiment is that nuclear transfer was successful in a primate, which is the order of animals that includes human beings.
The answers are "no" and "no." Dolly was bred at a research farm in Scotland. Scientists there are trying to find more efficient ways of raising farm animals with desired features. Cloning, or more specifically, nuclear transfer, would allow breeders to more quickly develop preferred traits in their animals. For example, they could pick out from a flock of hens the one that lays the most eggs. They could clone her and use the clones as breeding stock for future generations.
The rhesus monkeys were bred at a research center in Oregon. Their creators are trying to find a way to produce more suitable animal models for drug research. Nuclear transfer would allow them to make several genetically identical animals. Research studies could then be conducted with fewer animals because the variable of genetics would not affect study results.
There are many other reasons why researchers are keenly interested in nuclear transfer. For one, it may make it much easier to produce genetically engineered animals. Say for example that a farm has a pig that is excellent for breeding except for one flaw: it is prone to a particular disease. A cell from that pig could be removed and cultivated. The gene or genes leading to the disease could be removed or replaced. The genetic material from this revised pig cell could be used for nuclear transfer. The result: a more perfect pig.
Along the same lines, nuclear transfer also may make it easier to produce transgenic animals. As discussed in Chapter 6, there are many potential uses for transgenic animals. For example, say you want a cow that produces in its milk a human protein valuable as medicine. Let's review how such a cow is created now, to better understand how nuclear transfer could improve the process. First, you identify the human gene that directs the production of the desired protein. Then you splice this gene out of a human chromosome. You cultivate copies of the gene to inject into the nucleus of a recently fertilized cow egg. This egg is then cultivated into an embryo and implanted in a surrogate.
If the transplanted gene is successfully taken up by the egg cell's chromosomes, the calf that is born may be able to produce the desired protein in its milk. However, most times, the process fails. The egg does not develop into an embryo, the embryo does not continue into a fetus, or the fetus does not survive. Even if a calf is born, the desired gene may not appear in the chromosomes. When it does, it may not express itself properly.
Nuclear transfer could greatly improve the success rate. Copies of the desired gene could be injected into the nucleus of cultivated cells. Each cell could be examined to see if its chromosomes have taken up the gene. Only the cells that have successfully adopted the gene could be used for nuclear transfer. Breeding costs would be reduced because only calves carrying the desired gene would be raised. Of these calves, only the ones that successfully produce the protein would be bred for future generations.
Nuclear transfer technology also may contribute to a better understanding of what causes genes to express themselves within each cell. What is of particular interest is the ability to return cells to the "blank state" of an embryonic cell. This finding may lead to an understanding of how specific genes are triggered into action. Can we direct cells to turn "off" genes that lead to disease? Can we direct cells to turn "on" genes that aren't functioning? Can we stimulate the growth of new cells, for example, to replace ones that have been damaged? Can we slow down or reverse the aging process? These are the kinds of questions that nuclear transfer may help answer.
If this happens, it may well be to fulfill the desires of a person like Mrs. Fister, who is hoping to clone her dying child in order to keep a part of him alive. Other people may have equally urgent reasons for wanting to clone a child. If a couple is infertile, cloning could give them a genetically related baby. If a couple shares the same recessive genes for a disorder, cloning could give them a baby who won't inherit the disorder. (The baby would be a carrier, however, like the parent from whom it was cloned.) Females could use cloning in order to have a baby without involving any males. Males could use cloning to have a baby without involving any female (besides a surrogate mother). Some people with big egos may feel that the world deserves more of them. Others may wish for clones of sports heroes, celebrities, or gifted scholars. There are endless possible reasons people may have for wanting to clone a human being.
But what, exactly, are we talking about when we refer to a human clone? A clone would be a genetic equal of the original, like an identical twin. It would not, however, be the same person come again. If you were to clone Michael Jordan, you would not necessarily produce another basketball superstar. The clone would be born at a different time, raised differently, and shaped by different experiences. Such factors would affect the personality, physical condition, ambition, and destiny of Michael Jordan's clone more than his genetic heritage.
You also can't order a clone and have it delivered fully-grown to your door. A cloned human would have to grow up like everybody else. Before you learn whether Michael Jordan's clone can play basketball like the original, you would have to a wait a couple dozen years.
In a couple of ways a clone would be quite different from anyone who has come into the world so far. Babies as we know them now are a package of surprises. No one can state with certainty until after a baby is conceived whether it will be a boy or a girl or what other physical features it will have. But anyone who has a clone would know the genetic profile of the baby they were going to get before they got it.
Another way that a clone would be different is that he or she would be the immediate descendent of just one person, not two. It's an open question as to whom the parents of the clone would be. The original person from whom the clone was copied could be considered a parent. Or, that person could be considered the identical twin. The male and female whose chromosomes combined to make the original person could be considered the clone's parents. Or, they could be considered the grandparents. It depends on how you want to look at it.
All these factors need to be kept in mind as we consider Mrs. Fister's situation. If some doctor were able to grant her wish and make a clone of Junior, she would have to carry the baby for nine months before he was born and care for him for several years before he caught up to Junior's age.
This new child's circumstances would be quite different from those of the first Junior. For one thing, Junior II wouldn't have a father (both Mr. Fister and Junior I would be dead). For another, Mrs. Fister would be several years older than when she had her first boy. And of course, Mrs. Fister would have a very different set of expectations for Junior II than she had for Junior I.
These kinds of differences would affect Junior II's development in many ways that could never be predicted. Say for example that Mrs. Fister takes up an old smoking habit. This might trigger in Junior II an asthma problem that Junior I never had. Junior II may therefore be less athletic than Junior I. Or, he may be more athletic because he exercises more to increase his lung power. To give another example, say that out of a newfound fear of loss Mrs. Fister is more protective of Junior II than she was of Junior I. This may cause Junior II to be more timid than Junior I. Or, it may cause him to be more rebellious. No one can predict.
Neither can anyone predict how Junior II would be affected by the knowledge that he is a clone. Many adopted children are comfortable with the fact that they are not immediate genetic descendents of the people who raise them. So perhaps Junior II would not have a problem with his unusual genetic background. But perhaps he would. Perhaps he would feel that he was not wanted for himself.
Mrs. Fister also would not be able to predict her reaction to having a clone of the boy she is losing. She thinks she would love the second child because he is her link to others she has loved. And quite possibly she would care very dearly for the cloned child. But it also is possible that she would come to resent him because he is a constant reminder of what she has lost. The cloned child may not relieve her grief, in fact, his existence could mean that she can never move on from it.
Today's research into cloning is being done on animals, not humans. These experiments are very expensive and more often than not unsuccessful. In the Dolly experiment, for example, researchers tried 277 times to clone a sheep from mature cells but succeeded only once. Furthermore, new research on Dolly suggests that the molecules in the cloned 3-year-old sheeps' cells are behaving more like those of a six-year-old. Dolly, the cloned sheep, may be more likely to age prematurely because her genes were copied from a six-year-old sheep. It also is possible that clones from mature cells will have more genetic problems because of mutations to the original cell caused by exposure to carcinogens, viral infection, or simple aging. Because of the risks to embryos involved, many people believe that human cloning would be unethical and should be banned.
There are many reasons people give for such a ban. On reason is that cloning by definition means to make a copy, therefore, cloning undermines the right of every person to be valued for his or her uniqueness. Another reason against cloning is that it would lead away from the bonds between men and women. Yet another reason against cloning is that it is a form of genetic selection that leads quickly down a slippery slope into eugenics.
Some people are concerned that cloning would create complicated legal problems. For example, it could lead to custody battles between the different people who contribute a clone such as the egg donor, the nucleus donor, the genetic parents of the nucleus donor, and the woman who carries the fetus to term. Other legal issues would have to do with the rights of the person being cloned. In Mrs. Fister's case, there may be a question as to whether she has the right to decide to clone her dying child. That may be something only the child himself could decide, if he were conscious. And some might argue that no child should have to make such an enormous decision.
Or go back to the example of a celebrity like Michael Jordan. Say a star athlete gets bloodied in a tough basketball game. Can a fan rush down to the court, wipe up some blood, and run to a lab to have a clone made? In other words, once cells are removed from someone's body, does he have legal control over their use for cloning? Imagine another situation. An agent approaches a celebrity and convinces him that there is a huge potential market for his clones. The celebrity signs a contract to market his body tissues. Right now it's against the law for anyone to sell his or her organs. But could they sell their cells?
Though the support for a ban on human cloning is strong, there also are reasons against a total ban on research. One of the promises of nuclear transfer technology is that it might lead to new techniques for repairing skin burns, spinal cord injuries, and other organ damage. These benefits may never be realized unless cloning research using human cells is permitted. Such research could be limited so that the cloned cells do not divide to the stage where they are considered an embryo.
Other reasons against a ban have to do with our society's values. For example, our society is based on the "free enterprise system"-a marketplace of supply and demand. It can be argued that anyone who wants to invest in cloning research should be free to do so. If marketable products from this research are discovered, people should be free to sell them. And, if people want to spend money on cloning products, it's their business.
Our society also strongly supports the rights of individuals to have children. There already is great demand for IVF reproductive technology, which has helped many couples with fertility problems have children. There may therefore be significant pressure from the public for human cloning research because it could create even more opportunity for people to have genetically related offspring.
Finally, our society strongly believes in freedom of inquiry. There is the belief that the search for truth should not be restricted. According to this belief, society may choose to control how scientific findings are applied, but the research itself should be free to go forward. Along these lines, there is the concern that any ban on research would only force it underground. An alternative would be to regulate the research, but this leads to the questions of how to regulate it and whether regulation could control it.
These are just a few of the arguments, pro and con, in the dramatic debate over cloning. Public leaders, scientists, ethicists, and concerned citizens are now wrestling with the question of what to do with this "genie out of a bottle." There are no easy answers when ethical concerns clash with scientific discovery.
But you do have power. The way that society uses its knowledge of genetics will be shaped by the everyday choices its citizens make.
You help shape what happens through the way you express your beliefs and opinions and by the actions you take. You also affect what happens through your community efforts, working for the passage of laws or electing leaders who believe as you do.
You made a choice to gain some control of genetic issues by reading
this book. Now you have the choice to remain informed. You have the choice
to use your knowledge when making personal decisions that involve the use
of genetic research. And you have the choice to participate when issues
involving genetics are raised in your community.
|Table of Contents | Glossary|
Your Genes, Your Choices is a publication of Science + Literacy for Health, a project of the AAAS Directorate for Education and Human Resources. The publication was funded by the U.S. Department of Energy. The website was built by Mike Wooldridge. Send feedback to SciLi@aaats.org.