Chapter IV · The Genome

The Family,
Written in Code

Three generations, Grandpa John, Grandma Paula, and Dad Jon, each had their DNA read. Lined up together, their results do something no single test can: they show inheritance happening, gene by gene, and let us say exactly what Alice, Miles & Mason carry from the Tidd line.

JohnGrandpa
PaulaGrandma
JonDad
Alice · Miles · MasonThe kids
Five things the DNA reveals
🔓

A mystery in Dad's data, solved by his parents

Jon's own test failed to read his APOE gene (the big one for heart and brain aging), it came back as a no-call. But both grandparents read cleanly as ApoE ε3/ε3, the neutral, most-common type. Two ε3/ε3 parents can only have an ε3/ε3 child, so Jon's missing result is now certain: ε3/ε3. That's the power of testing a family, not a person.

🧬

The family signature: everyone carries "TT"

At TCF7L2, the single strongest common gene for type-2 diabetes, Grandpa, Grandma and Dad are all TT (two copies). Because Dad is TT, every one of his children inherits at least one T, guaranteed. It's a true family fingerprint, and a gentle, shared reason to keep an eye on sugar and stay active down the generations.

A longevity gene that survived every generation

At FOXO3, one of the only genes reliably linked to reaching 100, all three carry the favourable G "centenarian" variant. It passed from Grandpa and Grandma straight through to Dad, and stands a good chance of reaching the kids too. A small edge, but a real one, running clean through the line.

🐟

Why the family runs low on omega-3

At FADS1, both grandparents are carriers (one copy each) and Dad inherited both, making him a "slow converter" who turns plant omega-3 into the useful kind poorly. It directly explains his low omega-3 blood test. Practical upshot for the whole line: fish or algae oil beats flax.

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The autoimmune allele came down the Tidd side

At PTPN22, a master switch for autoimmune conditions, Dad carries one risk copy (A). Grandma Paula is GG, so she couldn't have supplied it: the A traces specifically to Grandpa John's side. It lines up with Jon's own borderline autoimmune blood markers, and it's exactly the kind of thing a family map makes visible that a solo test never could.

The Inheritance Ledger

Watch the alleles pass down.

Each person has two copies of every gene, one from each of their own parents. Every letter in Dad's column had to come from Grandpa or Grandma. Here it is, trait by trait.

Allele colours: ACGT (– = the chip couldn’t read that spot)
Passed to the next generation

What Alice, Miles & Mason
are guaranteed to carry from Dad

Wherever Dad has two identical copies, he can only pass that letter on, so every child receives at least one, no matter what their mother contributes. These four are locked in from the Tidd side:

TCF7L2 · "T"A shared, gentle nudge toward watching blood sugar, met easily with movement and diet.
FADS1 · "T"They’ll likely convert plant omega-3 poorly too, a reason to favour fish or algae oil early.
LCT · "G"The lactase "off-switch", some may find dairy sits less easily in adulthood.
FTO · "T" & ApoE ε3Good news: none of the three generations carry the FTO weight-risk allele, and the neutral ApoE ε3 line continues.
👁️

Light eyes run deep

At the main eye-colour gene, Dad and Grandpa both read GG, the light-eyed European variant, while Grandma is a brown-eyed carrier.

Fast on caffeine

Dad is a fast caffeine metaboliser (CYP1A2), coffee clears quickly. Grandpa carries one "slow" copy.

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Built for mixed sport

ACTN3 and COL5A1 put Dad in the middle, not a pure sprinter, and a hint of the tendon-injury variant he shares down the line.

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Clean on the big risks

No hemochromatosis (HFE), no Factor V clotting variant, no alcohol-flush gene, normal statin handling, reassuring across the family.

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The deep paternal line

The Tidd Y-chromosome almost certainly belongs to haplogroup R1b, the signature of Bronze-Age Britain, unbroken father-to-son for ~4,500 years.

🦴

A little Neanderthal

Like most people of European descent, the family genome carries roughly 2% Neanderthal DNA, a souvenir from Ice-Age Europe.

A careful word

These readings come from consumer DNA kits (23andMe), shared with the consent of each family member. They are informational, not medical advice, and consumer chips occasionally misread a spot. Nothing here should be used to diagnose or rule out any condition, that's a conversation for a doctor and, where it matters, a genetic counsellor. What this page is good for: wonder, connection, and a few smart, shared habits. Full method and caveats are in Sources.