(Image: Romann Ramsorn/Millennium Images)

SO ROMANTIC… when you kiss your partner passionately, not only do you exchange bacteria and mucus, you also impart some of your genetic code. No matter how fleeting the encounter, the DNA will hang around in their mouth for at least an hour. This means that women’s saliva could contain evidence of unwanted attention in cases of assault, or even telltale signs of infidelity.

Natália Kamodyová and her colleagues at Comenius University in Bratislava, Slovakia, recruited 12 couples who agreed to kiss each other passionately for at least 2 minutes. Afterwards, saliva samples were collected from the women at 5, 10, 30 and 60-minute intervals. Because Kamodyová’s method relies on detection of the Y chromosome, it can only be used to identify a man’s DNA in a woman’s saliva.

The results show that the man’s DNA was still present and could be detected through amplification after at least an hour, and possibly longer. “We’ve shown it’s possible to get a full profile, which could be useful in crime investigation to pinpoint the possible perpetrator among suspects or exclude those innocent,” says Kamodyová. Her team is investigating whether the DNA survives longer than an hour and whether it’s obtainable from the mouths of women who have died (Forensic Science International: Genetics, DOI: 10.1016/j.fsigen.2012.07.007).