It's never happened in the genetic testing industry or the dating industry. All you do is you spit in the cup, send the saliva back to the lab where we do our analysis, register your kit online, and do our psychological assessment. The second test we do is on a gene referred to as the serotonin reuptake transporter, and it really is a gene that involves how serotonin is processed in the brain.There are some really interesting studies from UC Berkeley where they looked at couples who were in a relationship for 10 years.

People who have the short version of this gene tend to respond more emotionally to negative and positive situations, while people with the long version of the gene tend to be more levelheaded.

What they found is if you have two married individuals who both share the short version of the gene, what you get is a level of affection that goes down over time.

"Above all physical factors — for example, how he looks — and social factors, how guys smell is more important than anything else," she said.

Holzle was not able to point to any success stories.

Basically, what I'm working with Singld Out to do is to have this data available to users when they go on the database.

In the future, we want to have a feature where you can search just based on the HLA scores [immune system genes] or just search based on the serotonin scores or the psychological assessment scores.

Some genetic testing companies are promising to match couples based on the DNA testing, touting the benefits of biological compatibility.

" said Eric Holzle, founder of Scientific, one of the first online dating sites to use DNA.

We have all the research that has been done on couples looking for biomarkers that can determine compatibility and why certain couples do better than others, and so we launched [Instant Chemistry] based on that, and started working with premium matchmakers, giving out kits.

We're really excited about our partnership [with Singld Out] because this is the first time anywhere that by joining a dating site you automatically get one of these kits in the mail, and that's something that's just revolutionary. The science is based around the concept that the more dissimilar two people are in terms of their immune system, the more attracted they tend to be to one another.

Holzle wouldn't reveal membership numbers, but Gene Partner, a Swiss company that works with matchmakers and dating sites, has tested more than 1,000 people, according to chief scientific officer Tamara Brown.