Dwarf Locus - Dw
The dwarf genetics are incompletely dominant (Fontanesi, 2021). To get a proper sized dwarf breed rabbit, you need one dwarf allele (“dw”) and one regular allele (expressed as “Dw”).
Dw: Dwarf
dw: Non-dwarf
Two regular alleles (DwDw) gives you a rabbit that is too large. These are called BUDs (Big Ugly Does) and BUB (Big Ugly Bucks). Two dwarf alleles (dwdw) gives you a peanut. Peanuts cannot metabolize food and will die within a week.
​If you breed a proper-sized (Dwdw) buck to proper-sized (Dwdw) doe, the buck can donate either a non-dwarf or a dwarf allele, and so can the doe. Therefore, some kits will get a non-dwarf allele from each parent, making it a BUD or a BUB. Some will get a dwarf allele from each, making it a peanut. Approximately half get one of each and end up as proper-sized.
If you breed a BUB to a BUD, all you can get is BUBs and BUDs because both parents can only donate a non-dwarf allele.
Since peanuts die at a very young age, you obviously cannot use them to breed so I will not explain what would happen IF they could be bred.
Breeding a BUB or a BUD to a correct dwarf results in the same chance of properly sized offspring but has no risk of peanuts.
Causative gene mutation is on the High-mobility group AT-hook 2 (HMGA2) gene. This gene acts as a factor in growth regulation during the development of the embryo (Hu, 2014).
"Peanut" Homozygous Dwarf
DwDw
Heterozygous dwarf rabbits are smaller size, rounder and blockier heads, shorter and thicker ears, and rounder shorter bodies.
Dwarf (heterozygous dwarf)
Dwdw
Peanuts are much smaller, have larger than normal heads, and their ears are smaller than normal and triangular. Their skulls are also deformed in shape. They are incompatible with life and do not make it past a few days.
Homozygous Non-Dwarf
dwdw
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Homozygous Non-Dwarf rabbits will be larger, have less rounded and smaller heads, have longer and typically more pointed/thinner ears, and longer bodies.