What Your Ancestry Test Is Actually Measuring
Ciara explains how consumer DNA tests estimate ancestry, why the percentages change when the company updates its reference panel, and what the results can and cannot tell you about who you are.
Two Brown-Eyed Parents, One Blue-Eyed Child
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Show notes
The eye colour myth
Most of us learned that brown beats blue in a neat two-by-two grid. Real eye colour involves at least sixteen genes and a lot of pigment chemistry. Ciara uses the example to explain how most traits really work, why the single-gene model persists, and how the same misunderstanding muddles conversations about inherited disease risk.
- The classic Punnett square and where it came from
- OCA2, HERC2 and the pigment dial
- Why two brown-eyed parents can have a blue-eyed child
- Polygenic traits and risk scores
- A genetic counsellor on how families hear the word recessive
Send your family tree mysteries to the Witspeak channel and Ciara will pick one for a future episode.
Transcript
Welcome back to Four Letters Long, I am Ciara Nolan. Here is a thing I have had to say gently many times. Yes, two brown-eyed parents can have a blue-eyed child, and no, that does not mean what you fear it means. The neat grid from school, brown beats blue, was a teaching tool that outlived its usefulness. Eye colour runs on at least sixteen genes and a pigment dial that turns rather than flips. Today I will walk you through the real version, and then show you why this matters far beyond eyes, because the same single-gene thinking muddles how families understand inherited illness. A genetic counsellor joins me to talk about what people hear when she says the word recessive. You are listening on Witspeak Podcasts. Look into my eyes, so to speak.
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