Blood type is inherited according to clear, though not always intuitive, genetic rules – which is why many parents are surprised when their child turns out to have a blood type seemingly different from either of theirs. The explanation lies in how the genes for types A, B, and O interact.
A person with type A blood can silently carry the gene for type O without knowing it – and if their partner carries the same hidden combination, the child can come out with a blood type completely different from both parents, without that meaning anything unusual genetically.
It’s a simple but elegant example of Mendelian genetics playing out directly in real life – “hidden,” recessive genes can skip an entire generation and resurface exactly when you least expect it.
A good reason to take a little extra time to understand how genetic inheritance actually works behind a seemingly ordinary lab result.
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