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When choosing a partner, should you consider his genes?

by Adrienne Dy, M.D.


Many say that dating is an art. Does the issue of genetic compatibility also make it a science? There is already a growing interest in its role in mate choice—which can make finding Mr. Right even harder. Any self-respecting lady scrutinizes a potential Prince Charming based on his appearance, mental prowess, ability to provide and interest-piquing personality; these days, she just might add “desirable genes” to the list.

But before we go knee-deep into the jargon, a crash course in genetics is in order.

The gene-ius of procreation

Deeply ingrained in our DNA, the genome contains the entirety of our hereditary information. From the Greek word for “I am born,” it is popularly known as the blueprint of life and is a lot like an instruction manual. Its sections, or chromosomes, contain paragraphs or genes. These are, in turn, composed of three-letter words that scientists call codons—permutations of four nucleotide bases: adenine, cytosine, guanine and thymine. There are an estimated 25,000 genes that “instruct” how to code for the proteins that make up our physical attributes and direct our bodily functions.

Genetic variation does not only make techniques like genetic fingerprinting possible, it also allows adaptation and survival. When genes confer a competitive advantage, natural selection enables the survival of the fittest.

Winning combination

From studying mate choice among primates, reptiles and insects, scientists have observed that females are often choosier than males. Some propose that they opt for mates with superior genes to ensure the greater fitness of their offspring. But the more widely accepted theory is that females choose males with whom they, as individuals, are more compatible with at the genetic level.

Among vertebrates, humans included, the role of a certain cluster of genes called the major histocompatibility complex (MHC) in mate choice has garnered a lot of interest. The MHC is in charge of encoding proteins involved in immune response, and has been credited for differences in individual susceptibility to parasites and disease. It has also been identified as a basis for kin recognition.

Experiments done on mice, rats and humans show that MHC correlates with mate selection. Under the concept of disassortative mating, test subjects have shown preference for partners with the most dissimilar MHC. Theoretically, better MHC variation would confer better defense against disease and ensure survival of progeny. To support this, it has been documented that in isolated human populations, couples with very similar MHC have significantly increased rates of fetal loss.

So far, we’ve established that genes do play a role in compatibility, but most of the “choosing” is done instinctively. What happens when this knowledge is harnessed more deliberately?

Recipe for perfection

The chilling scenario was demonstrated by the 1997 dystopian thriller, Gattaca, a movie set in the near future where technology is used to enhance human capabilities as desired by the offspring’s parents, creating “designer babies” and giving birth to genetic discrimination and prejudice.

That future is already unfolding in our present reality. Pre-implantation genetic diagnosis or embryo screening is currently being used abroad as an advanced form of prenatal diagnosis. Evaluation for potential genetic disease is done in vitro on embryos, prior to their implantation in the womb. This eliminates selective pregnancy termination, since the embryos that will be allowed to latch on and survive in the womb are those free of genetic problems.

Such powerful procedures carry with them the weight of ethical ambiguity. Locally, genetics is a relatively new field with less threatening applications. According to Eva Cutiongco-dela Paz, M.D., director of the Institute of Human Genetics of the National Institutes of Health in Manila, a focused type of genetic testing is done here. “We don’t do random testing,” she clarifies, “We do it for those with a priori risk, or a strong family history of genetic disorders.”

Genetic testing is the direct examination of the DNA to screen for genetic disorders. It can detect with significant accuracy if an individual is a carrier of a genetic condition. “Genetic information is changing the practice of medicine,” says Dr. Cutiongco-dela Paz. According to her, the most common reasons for consultation with geneticists are:

• poor obstetric history and infertility (“Is our failure to conceive because of genetic incompatibilities?”);

• having previous children with a genetic condition (“What are the chances that our next child will turn out the same?”); and

• couples themselves having a genetic disorder (“Will I pass this on to my child?”).

Dr. Cutiongco-dela Paz says that what makes genetic testing unique is that it is always accompanied by pre- and post-genetic counseling. “This touches on information that won’t only involve the individual at risk, but family members and future generations. This ... can also carry stigmatization, and possible discrimination for jobs, insurance.”

To know more about the role of genes in compatibility, get your copy of the Valentine issue of HealthToday magazine, out now in newsstands and bookstores.

Darwin in dating

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