Whether your roommate is Samantha Sleeps-Around or Paul the Prude, cut him or her some slack: People's predilections for promiscuity lie partially in their DNA, according to a new study.

A particular version of a dopamine receptor gene called DRD4 is linked to people's tendency toward both infidelity and uncommitted one-night stands, the researchers reported Nov. 30 in the online open-access journal PloS One.

The same gene has already been linked to alcoholism and gambling addiction, as well as less destructive thrills like a love of horror films. One study linked the gene to an openness to new social situations, which in turn correlated with political liberalism.

In the new study, researchers gathered a detailed history of sexual behavior and relationships from 181 young adults. They also collected DNA samples from the volunteers' cheeks and analyzed the samples for the presence of the thrill-seeking version of DRD4.

"What we found was that individuals with a certain variant of the DRD4 gene were more likely to have a history of uncommitted sex, including one-night stands and acts of infidelity," study researcher Justin Garcia, a postdoctoral fellow at Binghamton University, State University of New York, said in a statement.

"The motivation seems to stem from a system of pleasure and reward, which is where the release of dopamine comes in," Garcia said. "In cases of uncommitted sex, the risks are high, the rewards substantial and the motivation variable — all elements that ensure a dopamine 'rush.'"

People with the thrill-seeking gene variant were about twice as likely to report a history of one-night stands as those without the gene variant. Half of those with a love of risk imprinted in their DNA reported committing infidelity in the past, compared with 22 percent of those without the variant.

"The study doesn't let transgressors off the hook," said Garcia. "These relationships are associative, which means that not everyone with this genotype will have one-night stands or commit infidelity. Indeed, many people without this genotype still have one-night stands and commit infidelity. The study merely suggests that a much higher proportion of those with this genetic type are likely to engage in these behaviors."

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