How to distinguish a typical mouse? - briefly
A typical mouse is small (about 7–10 cm body length), has a pointed snout, beady eyes, prominent whiskers, and a long, hairless tail ending in a tiny tuft. Its fur is generally gray or brown, and it moves with rapid, scurrying motions.
How to distinguish a typical mouse? - in detail
A typical laboratory mouse can be identified by a combination of morphological, behavioral, and genetic markers that separate it from wild‑derived or specialized strains.
Physical characteristics include a compact body length of 6–10 cm, a tail roughly equal to or slightly longer than the torso, and a weight ranging from 18 to 30 g. The coat is usually short, uniform in color—commonly albino (white with pink eyes) or agouti (brown‑gray with a darker dorsal stripe). Ears are proportionally large, hairless, and positioned laterally on the skull. The facial whiskers (vibrissae) are long, symmetrical, and extend forward from the muzzle.
Key diagnostic features are:
- Skull morphology: Rounded cranium, short nasal bones, and a well‑defined zygomatic arch.
- Dentition: Incisors that grow continuously, with enamel restricted to the front surface, creating a chisel‑shaped edge.
- Reproductive traits: Short gestation (19–21 days), large litters (5–12 pups), and rapid sexual maturity (6–8 weeks).
Behavioral cues are equally informative. Typical mice display nocturnal activity patterns, preferring dark, enclosed spaces. They exhibit stereotyped exploratory behavior, such as rearing on hind legs and frequent grooming. In a standard open‑field test, they travel distances of 30–50 m within a 10‑minute session, showing thigmotaxis (preference for the periphery).
Genetic screening provides definitive confirmation. The presence of the C57BL/6 genetic background, identified through polymerase chain reaction (PCR) markers or single‑nucleotide polymorphism (SNP) panels, correlates strongly with the standard laboratory phenotype. Absence of mutations in the Lepr or Ob genes further distinguishes the common strain from metabolic disease models.
When assessing an unknown specimen, follow this procedure:
- Measure body length, tail length, and weight; compare to established ranges.
- Examine coat color and texture; note the presence of a dorsal stripe or albinism.
- Inspect ear size, whisker arrangement, and skull shape using a stereomicroscope.
- Conduct a brief behavioral observation in a low‑light arena to verify nocturnal activity and grooming frequency.
- Collect a tissue sample (e.g., ear punch) for DNA extraction and run PCR assays targeting strain‑specific markers.
By integrating these morphological, behavioral, and molecular criteria, one can reliably differentiate a standard laboratory mouse from other rodent varieties.