CALCBIOME — ISOPOD GENETICS

Which morphs will the babies be?

Pick the morph and both parents: the calculator gives the percentage of visual, het and normal offspring, for one or two genes at once.

MENDEL’S LAWSExact probabilities, not estimates.
DOCUMENTED MORPHSOnly those with known inheritance.
PRIVATEFree, no account. Your settings stay on your device.

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Result

Isopod genetics: the basics

Recessive: it takes 2 copies to show the morph. A het (carrier) looks normal but passes the gene to half its babies.
Possible het: normal-looking babies from two hets are het 66% of the time; from a het and a normal, 50%.
Co-dominant (Lava): one copy is enough to show the morph.
Two genes: Orange and Dalmatian in P. scaber are inherited separately: two double hets give 1 Orange Dalmatian baby in 16.
Breeding true: to get 100% visuals, pair two visuals of the same morph.

Examples with one recessive gene (Orange)

Parent 1	Parent 2	Visual babies	Normal babies that are het
Visual	Normal (not het)	0%	100%
Het (carrier)	Het (carrier)	25%	67%
Visual	Het (carrier)	50%	100%
Visual	Visual	100%	—
66% possible het	66% possible het	11.1%	50%

Inheritance from A. vulgare studies and crosses reported by breeders. If your results differ, tell me.

How we calculate

Each parent passes on one copy of the gene at random. The chance it passes the mutant copy is 0 (normal), 0.5 (het), 1 (visual), 0.25 (50% possible het) or 1/3 (66% possible het).
Visual babies (recessive gene) = p₁ × p₂. Hets = p₁(1 − p₂) + p₂(1 − p₁).
Normal-looking hets = hets ÷ (1 − visuals): the breeders’ “50% het” or “66% het”.
Two genes: inherited separately, so probabilities multiply.
Lava (co-dominant): 1 copy = visible Lava, 2 copies = the 2-copy form.

Example

Two P. scaber het for Orange: 25% Orange babies, 75% normal-looking, of which 67% are het.

Sources: Hasegawa et al. (1997, Pigment Cell Research 10: 265), autosomal recessive albinism in Armadillidium vulgare; Howard (1962, Journal of Genetics 58: 29); breeder-reported crosses for P. scaber (Orange, Dalmatian: F1 all wild-type, F2 close to 9:3:3:1) and P. laevis (Smug Bug, Arachnoboards). Becking et al. (2017, Scientific Reports) for sex chromosomes and Wolbachia.

Frequently asked questions

What does “66% het” mean?

A normal-looking baby from two hets has a 2 in 3 chance of being het too. You can only tell by breeding it.

Does orange × normal give orange babies?

Not in the first generation: all babies look normal but are het. Breed them together (or back to the orange parent) to get oranges again.

Why is Calico not offered?

Its inheritance is not established: it looks line-bred over several generations rather than caused by a single gene.

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