The “Infidelity Gene”

John and Mary Smith met in college and married soon after graduation. They were lucky enough to find good jobs in the same area, bought a condo, and settled into a comfortable life.

Eventually John and Mary decided to start a family. They heard about DNA testing: a new family planning procedure using DNA samples to screen for possible genetic differences that could affect their child’s health and development. This sounded like a wise precaution, and they ordered the tests. When the results came back, John and Mary were relieved to learn that they each had a clean bill of genetic health as far as their future children were concerned. There was one personal glitch, however: the tests revealed that John had the “infidelity gene.”

Mary had never heard of an infidelity gene. In fact, Mary wasn’t entirely sure what a gene was, and she had no idea how—or whether—a gene could cause her husband to be unfaithful. Mary consulted her doctor and searched online to find out more about this gene, but what she read was confusing. The following is a sample of her findings.

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The term “infidelity gene” is the popular name for a gene called AVPR1a. (The names of human genes are always capitalized and italicized.) AVPR1a controls the production of a protein known as the arginine vasopressin receptor. This protein is found on the membranes of nerve cells in the brain and is responsible for transporting the hormone arginine vasopressin from the bloodstream to the nerve cell. Several versions of the AVPR1a gene are found in humans. Different versions of the same gene are called alleles. John’s particular allele of AVPR1a made less protein than other alleles, which means that less of the hormone made it to John’s brain cells. Some scientists conclude that less hormone means less interest in a mate, which could lead to infidelity.

Mary understood very little of what she learned about AVPR1a. How do genes control protein production? What are hormones? Why do hormones need receptors? What do hormones do inside your brain? The one thing Mary did understand, however, was that scientific studies showed that males with this particular allele of AVPR1a are more likely to commit adultery. Was their marriage in trouble?


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