In the rabbit (Oryctolagus cuniculus), lethal dwarfism occurs in individuals homozygous for the dwarf allele (dwdw).
[1][2] Homozygosity for the dwarf allele results in a lethal autosomal recessive mutation.
[1] These individuals homozygous for the dwarf allele are viable in the womb but die days after being born.
[1] It was not until much later that rabbits solely as pets gained popularity, and as they did, breeding for smaller size became more prevalent.
[citation needed] Dwarfs owe their small size and features to both the dwarf allele (dw) and selective breeding,[1] where rabbits are selected by humans for their characteristics, resulting in more offspring of the desired characteristic.
[1] Kits (rabbit young) homozygous for the dwarf allele (dwdw) are often referred to as "peanuts", and although viable up to birth, die days afterwards.
The dwarf allele has been shown to have a genetic linkage with the Agouti gene, pointing to its presence on chromosome 4.
[citation needed] In rabbits, HMGA2 regulates growth of embryos and has been associated with mitochondrial function.