Natural gene / health
CVM (cervical vertebral malformation)
The neck vertebrae form crooked and pinch the spinal cord passing through them — the “wobbler” presentation, modelled here in its severe early-lethal form.
Crossing two of them
Born, and then lost
Lethal at birth, so the foal really is born: it gets a name, a record and a place in the family tree, and then dies over a few seconds with a chat line naming what took it.
That is deliberate. A pairing that silently produced nothing would teach a player nothing about the two horses they just bred, and the whole value of a recessive lethal is that it tells you something about both parents at once. The mechanics of the death are on the trait system page.
Its gene carrot
There is none. A disorder locus sets hasGeneCarrot() false —
forcing one onto somebody’s line is hostile — and
SpliceSafety keeps it out of the random splice as well, derived from
the fact that it declares a non-informational Condition rather than
from any hand-written list.
- Gene key
- horsegenetics.cvm
- Priority
- 99
- Alleles
- cvm N
- Outcomes
- wild,
cvm-carrier,cervical-malformation - Coat effect
- none — every outcome is a wild type
- Default allele
- N
- Wild population
- 1.6% of founders carry one copy; none carries two
- 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 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 whole locus collapses into one catalogue
entry. What the gene actually does travels on
the trait system instead.
The combination table
| combination | outcome | effect |
|---|---|---|
N/N | wild type | nothing |
cvm/N | cvm-carrier | nothing — a completely normal horse |
cvm/cvm | cervical-malformation | −15 health, −0.05 speed, −0.28 jump — lethal at birth |
This one has no confirmed causal variant, and says so
Every other natural gene in the mod names a real locus with a real published
mutation behind it. CVM does not have one. It is a well-attested heritable
malformation with a strong breed concentration and no agreed single
gene, so the key here is the condition’s own name
(horsegenetics.cvm) rather than a gene symbol invented to look
respectable.
Treating it as one recessive locus is the mod’s simplification. It is written down here, and in the class Javadoc, so that a later reader does not go looking for the paper.
The alternative was to leave it out. It earns its place because the roadmap’s disorder table wants a spread of breeds represented, and because the simplification is honest at the level the mod models anything — every locus here is one gene, one number, one outcome. Megaesophagus is the other gene in this position.
The founder table lists only the clear horse and the carrier. A wild-caught horse is an adult that survived, so it can carry this and never have it, and the homozygote’s weight is simply absent from the table. The only way to produce an affected foal is to breed two carriers — which is the whole design: it is what makes a pedigree worth keeping, and what turns the carrier wording in the info panel from decoration into the difference between a breeding programme and a lottery.
common/genetics/genes/CvmGene.java