Why is the rat albino? - briefly
Albino rats possess mutations that inactivate the tyrosinase enzyme, halting melanin synthesis and producing white fur and pink eyes. The genetic defect eliminates pigment cells, resulting in the lack of coloration.
Why is the rat albino? - in detail
Albinism in rats results from disruptions in the melanin‑production pathway. The primary cause is a mutation in the gene that encodes tyrosinase, the enzyme that catalyzes the conversion of tyrosine to dopaquinone, the first step in melanin synthesis. When tyrosinase activity is absent or severely reduced, melanin cannot be formed, leading to a lack of pigment in the skin, fur, and eyes.
Additional genetic factors can contribute:
- Mutations in the Oca2 gene, affecting melanosome maturation.
- Defects in the Slc45a2 gene, impairing melanosomal pH regulation.
- Rare alleles of the Mitf gene, which control melanocyte development.
Albinism follows an autosomal recessive inheritance pattern. Two copies of the defective allele are required for the phenotype to appear. Heterozygous carriers possess normal pigmentation but can transmit the allele to offspring.
Phenotypic consequences include:
- White fur and pinkish skin due to visible blood vessels.
- Red or pink eyes caused by the absence of iris pigment, which also reduces visual acuity.
- Increased sensitivity to ultraviolet radiation because melanin no longer provides photoprotection.
In laboratory settings, albino rats are valuable for:
- Visualizing internal structures during surgical procedures.
- Studying ocular development and retinal disorders.
- Serving as a uniform genetic background for transgenic experiments.
Overall, the absence of functional tyrosinase, often accompanied by mutations in related pigmentation genes, explains the lack of pigment in albino rats and determines the associated physiological traits.