Why are laboratory mice white? - briefly
Laboratory mice are bred as albinos because the absence of pigment eliminates coat‑color variability, facilitating visual identification of genetic modifications and reducing background interference in experimental measurements. This uniformity improves reproducibility and data accuracy across studies.
Why are laboratory mice white? - in detail
Laboratory mice are commonly white because the strain most frequently used, C57BL/6, carries a mutation in the Tyrosinase gene that eliminates melanin production, resulting in an albino phenotype. This genetic alteration is stable, easily inherited, and does not affect the animals’ physiological functions, making the strain suitable for a wide range of experiments.
The white coat offers practical advantages:
- High contrast against typical cage bedding and equipment, facilitating visual inspection for health issues, injuries, or experimental markers.
- Simplified quantification of fluorescent or colorimetric reporters, as pigmented fur can obscure signal detection.
- Uniform background for imaging techniques such as MRI, PET, and optical microscopy, reducing variability introduced by differing coat colors.
- Standardization across research facilities; a single, well‑characterized genotype ensures reproducibility of results and simplifies breeding programs.
Breeding programs maintain the albino trait through selective mating, preserving homozygosity for the Tyrosinase mutation. Because the mutation is recessive, crossing with pigmented strains produces heterozygous offspring that retain normal melanin synthesis, allowing researchers to generate pigmented cohorts when required without compromising the core white colony.
In summary, the lack of pigmentation in the dominant laboratory mouse strain arises from a specific genetic mutation that is easy to propagate, does not interfere with experimental outcomes, and provides visual and technical benefits that enhance data quality and animal welfare.