If you’ve ever heard doctors toss around “dominant” or “recessive,” you might have tuned out — but the difference is crucial to understanding genetic disease and why carrier screening matters. Let’s make this as simple as passing salt at dinner.
Dominant inheritance:
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You only need one changed copy of a gene to show symptoms.
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Think of it like a light switch — flip just one switch, and the light turns on.
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Example: Huntington’s disease. If you inherit it from either parent, you’ll develop it.
Recessive inheritance:
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You need two changed copies (one from each parent) to have the condition.
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With only one copy, you’re a carrier — the other “healthy” copy covers for it.
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Example: Tay-Sachs, cystic fibrosis, Gaucher disease.
At the dinner table:
Imagine each parent brings a dish. If both parents bring salad, you only eat salad (no main course). That’s recessive inheritance — both copies matter. If just one parent brings something spicy and overpowering, the whole meal tastes spicy — that’s dominant inheritance.
Why this matters for screening:
Carrier screening focuses on recessive conditions. That’s where two silent carriers can suddenly face a 1-in-4 chance of an affected child.
Dominant conditions are often easier to spot in family history — if one parent has it, it tends to show up. Recessive ones hide until the right match comes along.
Takeaway: Dominant = one copy is enough. Recessive = both copies needed. Screening helps reveal the hidden risks you’d never see from family history alone.