A 32-year-old woman from California has been sentenced to over four years in jail for being involved in a sex tape with her son with whom she was reunited after 15 years.

Mistie Rebecca Atkinson said the relationship with her son was not incest but a case of "genetic attraction", the 'Daily Mail' reported.

She was sentenced to four years and eight months behind bars by a court in Napa county.

The woman was reportedly found in a motel room in Ukiah, California, with her 16-year-old son who had recorded on his phone his mother giving him oral sex, as well as having sex with him.

Authorities also found nude photos Atkinson had sent her son, after they tracked him down through Facebook.

Atkinson told the court she did not consider it incest. "I don't feel like I should have the charge of incest because there is something called genetic attraction that is a very powerful that happens to 50 per cent of people becoming reunited with a long-lost relative," she said.

Atkinson reportedly had no contact with her son until last year, when she began sending him inappropriate messages on the social networking website, the daily said.

The boy was living with his father but was aware that Atkinson was his mother. She did not have custody rights for him.

The sexual contact began after there were reports of domestic violence between Atkinson and her live-in boyfriend in Nice, California.