How Designer Children Work

By: Kevin Bonsor & Julia Layton
Can your baby be everything you wished for?
Can your baby be everything you wished for?

Given the choice, would you rather have been born with a different eye color, hair color or ­skin tone? Maybe you would have chosen to be taller, thinner or more muscular. Of course, you didn't have these options. The physical and personal traits a person winds up with are just one big roll of the dice, with only the biological parents' genes to draw from. However, within advances in genetics research, people may soon preselect their children's physical and personality traits like they pick out options on a new car. ­

­Scientists have only begun to unravel the secrets hidden within the human genome -- the genetic blueprint for a human being. The mapping of the genome was finished in 2003, and scientists are continuing on the quest to discover what each gene does and how it functions. At this point in 2010, it's possible to manipulate the genes of embryos. In February 2009, a fertility clinic in Los Angeles tried to offer selection of hair and eye color but retracted the offering in the face of public backlash.


But the implications of human genetic manipulation go further than choosing green eyes. In England, deaf activists protested a 2007 bill that allowed for genetic selection only against certain diseases and disabilities, and prohibit selection for them, claiming deaf parents should have the right to select a deaf child if hearing parents have the right to select a hearing child [source: TimesOnline].

That same bill let parents select embryos that would make suitable "savior siblings" -- children conceived with the initial purpose of acting as donors for a sick brother or sister. Some people argue that embryos selected for their tissue types are a kind of designer children, just like embryos selected for tallness or blond hair.

Designing our babies is a reality that governments, ethicists and religious organizations are just now starting to address in full force. In this article, we'll learn about the progress and goals of human-genome research, how we're already weeding out genetic diseases and about the future of "selecting" human offspring.

The basis of all potential genetic manipulation in human beings is the human genome, the Holy Grail of genetics research. In 2003, scientists finished it -- at least to the degree that current technology allows.

Mapping the Human Genome

Human genes are found in the rungs of a DNA double helix. DNA makes up the 23 pairs of chromosomes in the human body.
Photo courtesy DOE Joint Genome Institute

If you think of the human body as big, complicated, encrypted code, then the scient­ists mapping the human genome are attempting to break that code. Once the code is broken, it will reveal many secrets of how the human body works, and it could lead to greater disease prevention. In June 2000, scientists from the Human Genome Project and from Celera Genomics both announced that they had assembled a working draft sequence of the human genome, a major step in cracking the code.

What researchers are trying to do is construct a detailed genetic map of the human genome and determine the entire nucleotide sequence of human deoxyribonucleic acid (DNA). A nucleotide is the basic unit of nucleic acid, which is found in the 23 pairs of chromosomes in the human body. According to the Human Genome Project, there are between 26,000 and 40,000 genes in the human body. Each of these genes is composed of a unique sequence of pairs, each with four bases, called base pairs.


In a DNA molecule, which is shaped like a twisted ladder, the bases are the chemicals that interlock to form the rungs of the ladder. The sides of the ladder are made of sugar and phosphate molecules. The human body has about 3 billion base pairs, but only about 4 percent of those pairs constitute DNA that affects gene function. We don't have any idea about the purpose of the other 96 percent of base pairs, consequently termed junk-DNA.

The finished sequence was completed, with 99.99-percent accuracy, in 2003. Discovering the secrets of the sequence is still in its infancy.

Better understanding the human genome will tell us a lot about how life works. It could lead to preventing or curing diseases, because genetics is what getting sick is all about -- our genes are trying to fight off the genes of a virus or bacteria. The next step will be to determine how this battle is played out. Today, researchers know the positions of some genes that control our medical traits. Other genes have been located but their functions are unknown, and still others remain entirely elusive. The point of genome research is to locate the genes and determine just how the four bases are sequenced, and then to learn what the genes actually do…

… which opens the door to all sorts of options.

Genetic Prescreening

Preimplantation genetic diagnosis involves screening embryos for genetic defects.


When doctors first performed in vitro fertilization (IVF) in 1978, it gave many otherwise infertile couples a way to have a child of their own. IVF works by removing the eggs from the woman's uterus, fertilizing them in a laboratory and then, a few days later, transferring the fertilized egg, called a zygote, back into the uterus. IVF has also led to a procedure that allows parents to weed out genetically defective embryos. This procedure is called preimplantation genetic diagnosis (PGD).


PGD is often used during IVF to test an embryo for genetic disorders before inserting it into the woman's uterus. Once the egg is fertilized, a cell from each embryo is taken and examined under a microscope for signs of genetic disorders. Many couples use this procedure if there are any inherited disorders in their genes to decrease the possibility that the disorder will passed to their child. Currently, PGD can be used to detect many disorders, including cystic fibrosis, Down syndrome, Tay-Sachs disease and hemophilia A.

Some genetic disorders are specific to one gender or another, such as hemophilia, which usually affects boys. Doctors may examine the cells to determine the gender of the embryo. In a case where a family has a history of hemophilia, only female embryos are selected for placement in the uterus. This practice is at the center of a larger debate about whether parents should be able to choose embryos purely on the basis of gender. Some people worry that it could lead to an imbalance between genders in the general population, especially in societies that favor boys over girls, such as China.

While PGD enables us to pick out embryos that don't have genetic disorders, and even chose the gender we want, it is only the beginning of what genetic engineering can do. Parents could some day custom-order babies with certain traits.

Hair- and eye-color selection is already a (highly controversial) possibility.

Choosing from the Genetic Menu

A baby playing
We'll be debating the boundaries of acceptable genetic manipulation for years to come.
Photo courtesy of Louisiana DHH

The idea of manipulating the genes of humans should not surprise us. Scientists have been altering animal genes for years. Goats and cows have been manipulated so that they produce more milk or more proteins in their milk. Mice have ­been injected with genes that may cause Alzheimer's disease in an effort to find a cure. Jellyfish genes have been injected into the monkey genome.

One of the more interesting transgenic animals was created by injecting a spider gene into a goat's genome. Spider silk is very strong and, if produced in enough quantity, could create a very powerful type of body armor. And while spiders don't make enough silk to produce this super body armor, scientists discovered that spider silk is a protein similar to goat milk. When the spider gene is inserted into a goat, the goat produces a protein that is identical to that found in spider silk. This protein is extracted from the goat's milk to produce silk fibers, called BioSteel, which is used to make bulletproof vests.


Altering the genetic properties of living animals is a reality, and some of these animals have genetic makeups similar to that of humans. It's only a small leap from here to producing humans who can jump higher, see farther, hear better (or not at all) or run faster. Before these super humans can be created, though, we have to learn more about the human genetic code.

One method that could soon be used to change human genetics is called germline gene therapy. It involves adding a step to preimplantation genetic diagnosis. Germinal cells are our reproductive cells, and this approach means manipulating genes of the sperm, egg or early embryo. Beyond just screening embryos, germline therapy actually adds new genes to the cells. It's possible that almost any trait could be added to an embryo to create a tailor-made child.

Germline therapy is already being performed on animals. Genetic changes to germinal cells may not show up in the animal that results from the embryo, but may instead show up in later generations.

The long-term implications of germline therapy could be the elimination of disease and disability by simply "fixing" genetic problems as they arise. They could also be a bit darker -- a "Gattaca"-esque scenario in which only genetically perfect beings can advance in society. Or a nation develops super-human bullet-proof speedster soldiers and conquers the rest of the world for slave labor.

Either way, we can look forward to intense debate in the coming years over the acceptable applications of genetics discoveries. Will designing children to look, act and think a certain way become a commonplace approach to propagation?

Lots More Information

Related HowStuffWorks Articles

More Great Links

  • Keim, Brandon. "Designer Babies: A Right to Choose?" Wired. March 9, 2009.
  • Le Page, Michael. "Fears over 'designer' babies leave children suffering." NewScientist. March 21, 2009.
  • Naik, Guatam. "A Baby, Please. Blond, Freckles - Hold the Colic." The Wall Street Journal. Feb. 12, 2009.
  • Savior siblings - the controversy and the technique. Telegraph. Aug. 10, 2009.
  • Templeton, Sarah-Kate. "Deaf demand right to designer deaf children." TimesOnline. Dec. 23, 2007.