Lethal Mutations

Three lethal mutations, Hereditary Multiple Malformation (HMM), Stumpy Limb (micromellia) and Short Beak present very similar in Coturnix quail, with all of them being lethal in homozygous form and indetectable in heterozygous form. It has been suggested that these are separate mutations due to dissections of the embryo (1)(2)(3), but this has been confirmed through test breeding (which is impossible), or gene sequencing. They are lumped together here because it would not make a difference for backyard breeders or geneticists.

All of the mutations cause the growing quail to die as an embryo. In HMM, the embryos tend to die at 5-6 days of incubation (3). Those that survive the first week die by day 15, with extra toes, shortened beaks, and no developed feathers or wings, with severely underdeveloped bone structure as well (3). It is the only mutation currently known to cause extra toes in quail (4). No birds with HMM are able to survive.

With Stumpy Limb (micromellia), embryos typically die around 15 days of incubation (2). It causes the bird to have abnormally short, parrot-like beaks if the bottom mandible develops, with normal length of body but shortened wings and feet (5). The bones in the neck and legs are also abnormally thick (2). Micromellia also causes bulging eyes, with an incorrectly developed digestive system (5).

Embryos with Short Beak also causes lots of defects. It presents very similar to Stumpy Limb and micromellia, with short and thickened leg bones, though the beak was wider and more developed (1). It is possible that chicks with Short Beak can hatch, though the chicks that do are severely deformed and typically die within three days (1). Embryos that die tend to be underweight, while the chicks that do hatch are on par with the wildtype chicks (1). The study was able to get 16 birds out of 600+ eggs set to reach sexual maturity, and those that did were fertile. It was test bred and proven to be a separate mutation from Stumpy Limb.

There are likely additional lethal mutations in Coturnix quail that are recessive (see: neck mutation here). These are just some of the better-studied ones. It is unlikely that they are in public hands, though it isn't certain because heterozygous birds can pass the gene down without anyone knowing, and few backyard breeders test every dead embryo. There are also many factors outside of genetics that impact embryo development and are much more prevalent, including incorrect humidity and temperature in incubators, and inconsistent environment and food sources in parents.

Breeding with Lethal Mutations:

Note: it is impossible to breed with any homozygous lethal gene, because the chicks die before they are able to hit maturity.

Het. Lethal x Het. Lethal = 25% Dead in Shell, 50% Het. Lethal, 25% Normal

Het. Lethal x Wildtype = 50% Het. Lethal, 50% Normal