A biology student got an unexpected lesson recently, when she found out about her mother’s infidelity through a blood-type discussion given in class.

The biology class, given at California State University, was about the characteristics of blood-types and how they are passed down from generation to generation. They were practising using a Punnett square, which is a diagram that is used to predict an outcome of a particular cross or breeding experiment. The student was reportedly confused as to why her blood-type was AB when her mother’s was A and her father’s O. This is an impossible occurrence, as the A and B genes are dominant and the O gene is recessive. So, as in this example, if an O gene is paired with an A gene, the blood type will be A.

The teacher, sure there was a mistake somewhere, asked the student to go home and confirm that all blood-types were correct. She did, and came back with an incredible revelation that took incredible courage to tell to the entire class.

The entire episode was tweeted by her classmate in a thread that has gone wildly viral. Scroll down below to check it out for yourself, and let us know what you think in the comments!

A Punnett square is a diagram that is used to predict the outcome of a particular cross or breeding experiment

Image credits: quora

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