Magical gene / ground and strong white

Fracture

Overo read backwards - a white horse with the coat colour breaking through it in hard-edged, unpredictable blocks and streaks. A third allele carries the same marking worked in greys instead of white - dark where the pale form is light, and the same number of steps.

What it can come out as

OutcomeCarrying
FractureFdf/Fdf · Fdf/Fdc · Fdf/Fdk
Black FractureFdk/Fdk · Fdk/Fdc · Fdk/n
Coloured FractureFdc/Fdc
Fracture carrierFdf/n · Fdc/n
Wild typen/n

How each one is actually drawn - region by region, and the layers it is built from - is on the coding tab.

Crossing two of them

Finding one

About 1 in 1,786 wild horses is born showing this. That is the whole of the supply: catch one, or make one with the carrot below. Breeds set their own pools and a breed built around this gene will carry it far more often than the wild population does.

Wild pairShows asHow often
Fdf/FdfFracture0.04% — 1 in 2,500
Fdf/FdkFracture0.0027% — 1 in 37,495
Fdf/FdcFracture0.0027% — 1 in 37,495
Fdk/FdkBlack Fracture0.0027% — 1 in 37,495
Fdk/FdcBlack Fracture0.0027% — 1 in 37,495
Fdk/nBlack Fracture0.0027% — 1 in 37,495
Fdc/FdcColoured Fracture0.0027% — 1 in 37,495
n/nWild type99.944%

Its gene carrot

The file

common/src/main/resources/horsegenetics/genes/fracture.json — a data-driven gene, not a Java class. It is listed in the index.json beside it and registered by Genes' class initialiser at startup.

Keyhorsegenetics.fracture
Phasemagical — it adds signed colour in phase 3, after the pigment has resolved
Priority201 — where it sits in the one (priority, key) paint order
AllelesFdf · Fdk · Fdc · n
Varies per horse4 values drawn once off the expressing allele copy, so a foal that inherits the copy inherits the look
Built fromPARTS, PATCHES, STROKES, TOWARD

Why it is built this way

The black allele is the white one with the light taken out of it, and it sits one rung under white in the dominance series - so every combination that existed before it keeps the outcome it had, and only the pairs carrying Fdk are new. The re-toning is a mapping rather than a repaint: every achromatic target moves into the dark end of the scale keeping its order and its spacing, and every SATURATED one is left alone, because that colour is the gene rather than its lightness.

What it paints

Each outcome, described the way the gene file describes it, and then the layers that draw it in the order they are painted. The prose is the part a reader checks a bake against; the list underneath is what the engine actually did.

Fracture

Instead of white appearing on a coloured horse, the colour appears on a white one - and it does it in bold uneven blocks and streaks with jagged edges, anywhere at all: neck, shoulder, barrel, hindquarter, legs, face. There is no symmetry to it and no pattern to predict; two Fracture horses out of the same parents look nothing like each other. The head usually keeps a distinct area of coat, and the mane and tail follow whatever is underneath them. It takes two copies - a single copy is carried and shows nothing.

  1. white over most of the horse — PARTS, painted with TOWARD
  2. the coat breaking back through it in blocks — PATCHES inverted × STROKES, painted with TOWARD

Black Fracture

The same marking as the white form with the light taken out of it: a single near-black tone.

  1. white over most of the horse — PARTS, painted with TOWARD
  2. the coat breaking back through it in blocks — PATCHES inverted × STROKES, painted with TOWARD

Coloured Fracture

The same fragmentation, with the ground in a colour the line carries rather than in white. Fully recessive: it takes two copies, and a single copy beside the white allele shows white. It never gives blue eyes, whatever the white form does.

  1. white over most of the horse, in colour — PARTS, painted with TOWARD
  2. the coat breaking back through it in blocks, in colour — PATCHES inverted × STROKES, painted with TOWARD

Fracture carrier

One copy shows nothing at all.

Paints nothing.

Wild type

No fracture.

Paints nothing.