
Description:
Downless is a double gene mutation in coturnix quail that causes the bird to hatch out with minimal to no feathering. It was originally discovered in 1971 at the University of New Hampshire by Dr. Savage and Dr. Collins (1). It shows up as chicks that are missing down or fluff at hatch. Some chicks will be "patchy", and others don't have any feathers or fluff. As chicks, they will be about the same size as fully downed and normal birds (1).
After a few molts, most chicks do grow in some feathering. Most quail with downless will appear completely normal as an adult, with complete feathering, though some birds will still miss patches of feathers towards the back and under wings at 21 days old (1). Males tested were proven to be sterile (3), and while females may still lay eggs, they will not lay nearly as many as their normal counterparts (1). It is unknown how fertile females are, though it is suggested that they still are able to produce offspring.
It is controlled by two separate recessive genes that work together to create the overall downless mutation (2)(3). This makes it incredibly difficult to track through different flocks. It was originally believed to only exist in a lab. However, recently, birds have been bred by Thieving Otter Farm that match the overall description of Downless as well as the affects of the gene. Because of this, it is suspected that the two recessive genes are in pubic hands and just very rare to be bred together.
The gene symbol is dl-1 and dl-2, and the order of dominance is Downless < Wildtype for both genes.
Breeding with Downless:
Downless x Downless = 100% Downless, though - no chicks hatch or develop as males are infertile.
Downless male x Normal = No egg development
Downless female x Normal = 100% het. dl1, het. dl2, (appears normal, titled F1 here).
References & Further Reading
Savage TF and Collins WM. Downless, a mutant in Japanese quail. Poultry Science, 50:1627 . 1971a
Tsudzuki, Masaoki. "Mutations of Japanese quail (Coturnix japonica) and recent advances of molecular genetics for this species." The journal of poultry science 45.3 (2008): 159-179.
Fulton JE, Roberts CW, Nichols CR, Cheng KM. Short barb: a feather structure mutation in Japanese quail. Poult Sci. 1982 Dec;61(12):2319-21. doi: 10.3382/ps.0612319. PMID: 7163112.
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