Natural gene / performance
PDK4
Racing performance, as one atomic gene. Each A
copy is worth 0.018 movement speed, and nothing else.
What it does
What it does: makes the horse faster, and nothing else. It changes no part of how the horse looks.
It is one of three speed genes, so a genuinely fast horse wants all of them.
Crossing two of them
Its gene carrot
- Gene key
- horsegenetics.pdk4
- Priority
- 81
- Alleles
- A G
- Outcomes
pdk4-fast,pdk4-mixed,pdk4-plain- Coat effect
- none — every outcome is a wild type
- Default allele
- G
- Wild population
- p(A) = 0.25
- Founder draws
- 1 × nextFloat()
- Catalogue entries
- 1 — it never changes what a horse looks like
Every combination of this gene is an expression
marked wildType. That reads oddly for a gene that can change how
big a horse is or kill a foal, and it is exactly right: wildType
means changes nothing about the coat. Because none of the non-coat
genes paints, Gene.affectsCoat() is false for all of them, they
are left out of a horse’s texture key, and the
genotype gallery collapses the whole locus into one
entry however many alleles it has. What the gene actually does travels on
the trait system instead.
The combination table
| combination | outcome | speed |
|---|---|---|
A/A | pdk4-fast | +0.036 |
A/G | pdk4-mixed | +0.018 |
G/G | pdk4-plain | — |
Why one gene and not a marker set
In reality this is one marker in a cluster, and racing ability is a polygenic
sum over many of them. Polygenic inheritance is cut from this
mod (a settled decision),
and the reason is a design one rather than a technical one: a hidden sum of
anonymous markers is indistinguishable from a dice roll at the scale a
player can observe, and the whole point of the genetics here is that a player can
breed for something and see it work. So the cluster collapses into two
alleles with an additive weight, and a player who fixes A/A in a
line has visibly made it faster.
Together with MSTN and CKM
it makes speed a three-locus breeding problem rather than a single switch: the
fastest horse the model can make is 0.3135, against a baseline of
0.1875 and a vanilla range of 0.1125–0.3375.
common/genetics/genes/Pdk4Gene.java