Is the “yellow mouse” mutation known to be inherited as a dominant autosomal trait? - briefly
The classic yellow coat allele in mice is X‑linked recessive, not an autosomal dominant trait. A distinct dominant yellow allele (Ay) does exist on an autosome, but it is a separate mutation.
Is the “yellow mouse” mutation known to be inherited as a dominant autosomal trait? - in detail
The yellow coat colour in laboratory mice results from a single‑gene alteration that follows an autosomal dominant pattern. Heterozygous individuals display the characteristic golden‑yellow fur, while the homozygous condition is embryonically lethal, preventing the appearance of a second phenotypic class. Consequently, crosses between a yellow mouse and a normal‑coloured partner produce offspring in an approximate 1 : 1 ratio of yellow to non‑yellow, with no correlation to the sex of the parents.
The mutation resides in the agouti signalling protein (ASIP) locus. A retroviral insertion or point mutation causes ectopic expression of ASIP in the dermal papillae, shifting melanin synthesis toward pheomelanin, which imparts the yellow hue. Molecular analyses have confirmed the presence of the inserted element in the ASIP promoter region, and RNA‑seq data show up‑regulated ASIP transcripts in skin samples from heterozygotes.
Breeding records from multiple laboratories corroborate the inheritance model:
- Crosses of Y/+ × +/+ yield 50 % Y/+ (yellow) and 50 % +/+ (normal) offspring.
- No yellow offspring arise from Y/Y matings because embryos fail to develop past early stages.
- The phenotype appears equally in male and female progeny, indicating autosomal—not sex‑linked—transmission.
These observations align with classic Mendelian expectations for a dominant autosomal allele with a recessive lethal homozygous state. The mutation has been employed as a phenotypic marker in genetic mapping and as a model for studying melanin pathway regulation.