A series of tweets has claimed that student discovered that her dad was not her biological father after she completed blood tests for a science class.

The girl, who is thought to be a student at California State University, purportedly realised that the man she thought was her father was actually her uncle, and in the process she uncovered the affair that her mother had.

Fellow student, Anya Hettich, took to Twitter to detail the events as they unfolded.

According to Hettich, the student was questioned by their professor after her blood type didn't correlate with that of her parents.

The student told the lecturer that her dad's blood type was O and her mum's was A, yet hers was AB.

The professor told her that this combination was impossible and asked her to speak to her parents to double check her information was correct.

According to Anya, the girl was "persistent that she wasn't wrong on the blood types and was confident that there was something wrong with how the prof was doing it."

At the next lecture, the professor asked the student about the blood types, which was when the revelation was relayed to the entire class of 243 pupils.

The girl explained that after speaking to her parents, her mother revealed that she had an affair with her husband's step-brother.

The mother had hidden this information for 21 years until the blood confusion revealed the truth. This meant that the girl had in fact been raised by her uncle rather than her biological father.

She then said that her legal parents were now filing for divorce in the wake of the discovery.