Where did white mice come from? - briefly
Albino laboratory mice descend from the common house mouse (Mus musculus), captured from wild populations and selectively bred for the recessive white‑coat allele. The principal lineage was established in the early 20th century for genetic research.
Where did white mice come from? - in detail
The white phenotype in Mus musculus results from a recessive allele ( alb ) that blocks melanin synthesis, producing a uniform pink‑skin, white‑fur appearance. This mutation occurs spontaneously in wild populations, though at low frequency, and has been documented in several geographic regions, including Europe, North America, and parts of Asia. Early natural specimens were collected by naturalists in the 19th century, providing the first evidence that albino individuals could survive in the wild.
Laboratory use began after the discovery of the alb allele in a British colony of house mice. In 1902, a breeder named C. C. Little identified an albino mouse in a stock of wild‑caught animals and established a breeding line by pairing homozygous carriers. The resulting strain, later designated “Swiss albino,” exhibited rapid reproductive cycles, high litter sizes, and a lack of pigment that facilitated visual observation of internal organs and experimental procedures.
Subsequent expansion of the strain involved:
- Crosses with other domestic lines to introduce genetic uniformity and reduce background variability.
- Inbreeding for more than 20 generations to achieve isogenic status, creating the widely used C57BL/6 J albino variant.
- Distribution to research institutions worldwide through commercial vendors, ensuring a standardized genetic background for biomedical studies.
Genetic analysis reveals that the alb allele is a point mutation in the tyrosinase gene ( Tyr ), which encodes the enzyme catalyzing the rate‑limiting step of melanin production. Homozygosity for this mutation eliminates enzymatic activity, resulting in the white coat and pink eyes characteristic of the strain.
Thus, the current laboratory white mouse originates from a naturally occurring albino mutation, captured in the early 20th century, subsequently refined through systematic inbreeding and global dissemination for scientific research.