Description:
Lethal yellow was one of the first ASIP genes discovered in Coturnix quail, and is linked with the lethal yellow agouti gene also found in mice (1)(2). In heterozygous form, the bird will look similar to Italian, with a description of "wheat, straw-colored" feathering. In homozygous form, the gene is lethal, and embryos will die within a few days of development (1). Any that do develop and hatch are generally weak and do not survive longer than a week (5).
The heterozygous form also has several health issues, including an increase of body fat, a 10% increase in overall mortality (1), a decrease in body temperature and weight gain, and overall less adaptable to stress (2). Because of this, it often wasn't used in lab testing and was never officially released in public hands.
This is a completely separate and unlinked gene to Fawn (often called fawn-2 in research papers), which causes Italian and Manchurian varieties of Coturnix. Though they look visually similar and share a loci, these are confirmed to be two different genes (3). Lethal Yellow again isn't found in public hands, and the Fawn that is currently available produces no health defects (3). It is similar to, if not the same gene as the Light Down referenced in a 1990's study (5).
In the order of dominance on the ASIP locus: Recessive Black is the most recessive, followed by Wildtype, then Lethal Yellow, with Fawn-2 being the most dominant gene (4).
Breeding with Lethal Yellow (Note: Yellow here is used to describe the heterozygous form)
For more information about breeding with this kind of gene, please see here.
Yellow x Wildtype = 50% Yellow, 50% Wildtype
Yellow x Yellow = 25% Wildtype, 50% Yellow, 25% Dead in Shell
References & Further Reading
C. W. Roberts and J. E. Fulton. 1980. YELLOW: A MUTANT PLUMAGE COLOR, SEGREGATING INDEPENDENTLY FROM BROWN, IN JAPANESE QUAIL. Canadian Journal of Genetics and Cytology. 22(3): 411-416. https://doi.org/10.1139/g80-050
Minvielle, Francis, et al. "Effects of the dominant lethal yellow mutation on reproduction, growth, feed consumption, body temperature, and body composition of the Japanese quail." Poultry Science 86.8 (2007): 1646-1650.
Tsudzuki, M., et al. "Fawn-2: a dominant plumage color mutation in Japanese quail." Journal of Heredity 87.3 (1996): 248-252.
Hiragaki, Takahiro, et al. "Recessive black is allelic to the yellow plumage locus in Japanese quail and associated with a frameshift deletion in the ASIP gene." Genetics 178.2 (2008): 771-775.
S. Ito, M. Tsudzuki, Light Down—Dominant Plumage Color Mutation with Homozygous Lethality in Japanese Quail, Journal of Heredity, Volume 84, Issue 3, May 1993, Pages 222–225, https://doi.org/10.1093/oxfordjournals.jhered.a111324
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