Look ma, no heteros: gay and lesbian couples could be giving birth to babies genetically related to both same-sex parents if current research pans out. (Science).

When Joanna Matthews hears people crooning over a baby, declaring that "he has his mother's eyes" or "she has her father's nose," she tends to cringe. Matthews, a lesbian who plans to someday start a family with her partner, knows that current fertilization capabilities allow only one of them to be a biological parent.

Artificial insemination, the use of egg donors and surrogate mothers, and even implanting an artificially inseminated egg from one partner into the womb of the other have helped fuel what is sometimes called the "gay-by boom." And yet despite these incredible scientific advances, one fundamental reproductive goal remains unattainable: children of gay and lesbian couples that reflect genetic characteristics of both partners. "We want what most people want: a mixture of our eye colors and hair colors, our personalities, and our physical features," says Matthews, who lives in Fredericksburg, Va. "But that's just not an option for us."

Not today, perhaps. But if early research under way in Chicago, New York City, Melbourne, and other sites around the world bears fruit, there may someday be "heterosexual-free" fertilization techniques that combine the chromosomes of two same-sex partners, resulting in embryos composed genetically from both men or both women.

Orly Lacham-Kaplan, a reproductive biologist at Monash University's Institute of Reproduction and Development in Melbourne, has spearheaded a study using DNA from any adult cell to fertilize a human egg. The process would work by inserting the nucleus of an adult's cell (which has 46 chromosomes) into a female egg, with its 23 chromosomes. Scientists then force the egg to begin dividing through chemical and electrical stimulation, which prompts the donor cell to eject half of its 46 chromosomes. The remaining 23 chromosomes pair up with the egg's 23 chromosomes, resulting in the formation of an embryo with half its genes coming from each parent. Lacham-Kaplan's team has performed this technique with mouse cells in lab tests, resulting in viable embryos, but has not yet implanted them into female mice.

In January scientists at the Reproductive Genetics Institute in Chicago reported that they successfully created mouse embryos using a similar method that removes half the chromosomes from the nucleus of an adult cell. The remaining half-complement of chromosomes is used to fertilize an egg. The results of early tests on human eggs are expected to be announced in April at the Fourth International Symposium on Preimplantation Genetics in Cyprus.

While this method requires at least one female partner, the reproductive conundrums faced by lesbian couples also apply to gay males, says Alan Ross, founder of the Gay Fathers Coalition International. Only one of the men in a couple can be a sperm donor, leaving his partner without genetic ties to their child. And gay men face the added burden of finding a female surrogate willing to carry the child to term and give birth.

"That brings up all kinds of legal and financial issues that must be taken care of up front, and that can be a long and difficult process," Ross says. "When you're a heterosexual, having a baby is just part of the formula. When you're a gay man, it's not so easy."

But researchers are attempting to remove some of the scientific barriers through technologies similar to those that may eventually permit lesbian couples to conceive children. Eleanor Nicoll, public affairs manager for the American Society for Reproductive Medicine, reports that scientists at the Weill Medical College of Cornell University in New York City are working on a method to replace the genetic material in a female egg cell with the nucleus of a 46-chromosome male cell. By inducing the nucleus to undergo meiosis--a process of cell division that reduces the 46 chromosomes by half--the male's DNA in the egg can then be fertilized by his partner's sperm, which also contains 23 chromosomes per cell.

Calum MacKellar, editor of the international journal Human Reproduction and Genetic Ethics, has suggested that the same technique also could use sperm DNA. This "male egg" could then be fertilized with sperm from the other partner, resulting in sperm-sperm reproduction. "I have already been asked by some gay couples to help them conceive a child with the `male-egg' technique," MacKellar says. He cautions that it could be years before such a procedure is available to same-sex partners.

Perhaps the most controversial reproductive technology being studied is cloning, says E. Scott Sills, director of oocyte donation at Georgia Reproductive Specialists in Atlanta. In simple terms, cloning is creating an exact genetic duplicate of a living animal.

Cloning is accomplished by first removing female DNA from an egg cell, Sills says. Then the nucleus of a 46-chromosome cell is extracted from the animal to be cloned, usually from a skin, muscle, or nerve cell, and is inserted into the egg. Through chemical and electrical stimulation, the egg begins to divide and grow.

This is the same technique used by British researchers in 1996 to create Dolly, a cloned sheep, and employed by Advanced Cell Technology in November 2001 to make a human embryo clone that grew to six cells in size.

For lesbians or gay men, of course, cloning would eliminate the outside donor but would produce a child genetically related only to one member of the same-sex couple, not both.

Furthermore, reproductive cloning is a hot-button issue, one that has led some doctors, researchers, and scientific groups, including the National Academy of Sciences, to call for its ban. The U.S. House of Representatives has already passed a measure banning human cloning, with the Senate expected to address the subject as early as this spring. Other countries are also examining the issue for possible regulation or prohibition.

But Suzanne Holland, an associate professor of religious and social ethics at the University of Puget Sound in Tacoma, Wash., isn't opposed to human cloning on religious or moral grounds. Instead, she refuses to back the procedure--or any of the other assisted reproduction methods being studied--until a proven safety record is established. "If it were safe for human beings, I wouldn't have a problem with using the technology, particularly if it were the only way for a couple to have a child," she says. "But it is absolutely unsafe now and for the foreseeable future."

Chief among the potential problems with cloning are physical and metabolic defects, says Ingrid Rodi, director of the Center for Reproductive Medicine at Century City Hospital in Los Angeles. Many of these, such as birth defects, would be immediately apparent, but others wouldn't be detected or wouldn't manifest themselves until long after the baby's birth, possibly even as late as puberty or adulthood.

These potential cloning problems also are likely to crop up in other reproduction methods that manipulate male or female genes, MacKellar says. "It is very likely that problems could affect children conceived in this way," he notes. "It is a very complex technique which is not yet fully understood."

While scientists continue to iron out the technological difficulties in achieving heterosexual-free reproduction, there is one major barrier that must be confronted directly by gay and lesbian couples who someday seek these services: cost. The price tag for currently available in vitro fertilization and surrogacy services can run as high as $50,000, Sills says. The costs of the various DNA techniques being researched could easily exceed that figure.

The slow pace of scientific research also poses problems of its own. None of the techniques described here is even remotely close to consumer availability, researchers say; this is at least a decade away. There's also a good chance none of them will pan out.

"The message is not to wait for this stuff to come along [to pursue parenthood]," Rodi says. But for couples such as Renee Sanford and April Espinosa of Hallandale, Fla., the legal hoops they currently have to jump through to have a child may make the cost and the wait worth enduring.

"Legally, in every aspect, the child would be mine and hers," Sanford says. "For that, I would consider waiting and doing my best to pay whatever it would take. Sure, the cost and the wait are drawbacks, but not to the point where it would discourage me."