Leo frowned. “But what if the old record is wrong? Blood typing isn’t perfect. Or what if Ana’s type changed? No—that doesn’t happen. Or what if—” He stopped. “Wait. What if Julian knows that? What if he’s counting on us not checking Ana’s historical type?”

After running the simulations, Maya’s group confirmed that a type O child can only come from a type O parent or a heterozygous A/O or B/O parent. Since Ana was OO, Julian’s father must have contributed an O allele. That means Julian’s biological father was either type O, A, or B—but not AB.

Her partner Leo leaned in. On the chart: Grandparents Ana and Carlos (both type A), their three children—Elena (type O), Marco (type AB), and Luis (type A)—and Luis’s two kids, Sofia (type A) and Diego (type B).

Here’s a short draft for a lab activity story titled Title: The Heirloom Type

“If Julian is truly Ana’s son,” Maya said slowly, “and Ana was AB at the time of his birth, Julian cannot be type O.”

When a rare blood type surfaces in a family pedigree, four lab partners must use serology and deductive reasoning to determine whether a long-lost relative’s inheritance claim is truth—or a clever lie. Story Draft