How did white mice appear? - briefly
White mice resulted from the intentional breeding of naturally occurring albino mutations, first isolated in laboratory rodent colonies in the early 1900s and propagated for research purposes. Their prevalence stems from the ease of maintaining the recessive allele that eliminates pigment production.
How did white mice appear? - in detail
The white coat of laboratory mice results from a recessive mutation in the Tyrosinase (Ty) gene, which disables melanin synthesis. The first documented albino mouse, named “Swiss” or “Swiss albino,” appeared in the early 1900s when breeders in the United States observed spontaneous coat-color changes in a mixed‑breed population. Genetic analysis confirmed that two copies of the defective Ty allele are required for the phenotype, making the trait easily fixed through inbreeding.
Breeders exploited the mutation for several reasons:
- Uniform coloration simplifies visual monitoring of experimental subjects.
- Lack of pigment reduces interference in studies involving skin or ocular physiology.
- Albino strains serve as genetic backgrounds for transgenic and knockout projects because they are well characterized.
The process of establishing a stable white line involved:
- Identifying an albino individual in a heterogeneous colony.
- Crossing the albino with a normal‑colored mouse to produce heterozygous offspring.
- Interbreeding heterozygotes to generate homozygous albinos (approximately 25 % of the litter).
- Repeating the cycle for multiple generations to achieve >99 % homozygosity, eliminating residual pigmentation alleles.
Subsequent research revealed additional mutations that enhance the phenotype, such as the c (coat color) locus, which suppresses any residual pigment deposition. Modern white laboratory mice, including the C57BL/6 J albino derivative and the BALB/c strain, are maintained as inbred lines with documented genetic backgrounds, ensuring reproducibility across biomedical studies.