The latest advances in stem-cell research mean someone could some day become a biological single parent, the source of both the egg and the sperm needed to make a baby.
"In theory, a single individual could be both mother and father to a child. The individual does not even have to be living if there is a stored sample of their cells," the University of Alberta's Tim Caulfield and his colleagues write in a paper in the journal Cell Stem Cell.
Their paper, The Challenge of Regulating Rapidly Changing Science: Stem Cell Legislation in Canada, documents how the speed and unpredictability of scientific advances in the stem-cell field pose a challenge to policy makers.
For example, scientists in a number of countries are now able to turn adult skin cells into stem cells. Once they have been reprogrammed, these cells regain the superhero-like powers of embryonic stem cells and can be turned into many of the specialized cells that make up the human body, including blood, brain or muscle cells.
But what if some of the reprogrammed stem cells originally taken from an individual were coaxed into becoming sperm, while others were transformed into eggs?
It hasn't happened yet, but research suggests it is possible, Dr. Caulfield says.
Egg and sperm created from stem cells from one person could be used to create an embryo, which could then be transferred to the womb of the mom-pop, or in the case of a pop-mom, a surrogate mother.
The result could be something "very strange and dangerous," warns Shinya Yamanaka, the Japanese stem-cell pioneer who discovered how to reprogram adult skin cells to stem cells. His breakthrough made headlines around the world in 2007.
Dr. Yamanaka's work, recognized this year with a prestigious Gairdner award, offered an alternative to research involving stem cells from aborted fetuses, which some people find repugnant on moral or religious grounds.
But it also raised other troubling possibilities about where stem-cell science could be heading, questions that both scientists and ethicists are now considering. Should biological single parenthood be allowed if it proves possible? What are the risks to a child created in this way? Could skin cells from one child be used to create another son or daughter? Could someone steal a skin cell from someone famous and have their baby?
It is a hot topic, Dr. Caulfield says, and an example of how it is difficult to design legislation that keeps up with the unpredictable advances in fields such as stem-cell research.
It is unclear, he and his colleagues say, if Canadian legislation governing reproductive technologies and embryonic stem-cell research would prohibit making sperm and egg from skin cells.
Canada's legislation bans the genetic altering of sperm or eggs.
Until last month, researchers reprogramming adult cells into stem cells did so by inserting a number of key genes that orchestrated the transformation to an embryonic-like state. That's a genetic alteration.
But now, Canadian scientists have found ways to get rid of any trace of those genes - which can cause cancer - once they have done their work. Is that a genetic alteration? Would it be covered by legislation if a stem cell derived from an adult skin cell was turned into sperm or egg? It might circumvent the ban, Dr. Caulfield and his colleagues say.
"It really shows how the approach of rigid rules and rigid legislation inevitably isn't going to work," Dr. Caulfield says.
Canada has one of the most restrictive laws governing stem cell-research of any pluralistic society with a wide mix of religious beliefs - and non-beliefs.
He argues that it is better to have a clearly articulated set of principles that a regulatory body could interpret as research moves in new directions.
A child created with egg and sperm derived from one person wouldn't be a clone - or genetically identical to the parent - because of the mixing and matching in the chromosomes that takes place when egg and sperm are formed.
Researchers have made substantial progress in coaxing stem cells to become sperm or eggs, work that could provide new treatment for infertility but that also opens the door to biological single parenthood.
In mammals, the primordial cells that become egg and sperm appear to be the same. But some researchers argue it would be easier to make an egg from a man's skin cell then to make sperm from a female skin cell. That's because cells from a female wouldn't have a Y chromosome, which may carry genes involved in the production of sperm.
In 2006, researchers at the University of Newcastle upon Tyne in Britain reported that they had transformed human stem cells into what are called primordial germ cells, which give rise to sperm or eggs. In mice, sperm derived from stem cells produced live pups.
In China, researchers recently reported that they had generated eggs from stem cells taken from the ovaries of mice.
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