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A Bit of Genetics

The Russian Blue & the Nebelung

A fascinating demonstration of how a single gene can transform a cat's appearance while maintaining an identical breed standard.

1. The Dilution Gene: The Secret Behind the 'Blue'

The Russian Blue and the Nebelung are genetically black cats. Their blue coat comes from the recessive dilution gene. d.

This gene modifies the distribution of melanin pigments in the hair, creating that highly characteristic slate-blue appearance.

Responsible genotype: dd

2. The FGF5 Gene: The Origin of the Nebelung

The main difference between the Russian Blue and the Nebelung lies in coat length, controlled by the FGF5 gene.

Russian Blue:

Short hair (dominant allele)

LL ou Ll
Nebelung :

Medium hair (recessive allele)

ll
A Russian Blue carrying the Ll genotype retains a short coat, but can pass on the long-hair gene to its offspring.

3. The Silver Tipping

The silvery sheen of the coat does not come directly from a color gene, but from the structure of the hair itself.

The tip of the hair shaft contains minimal pigment, allowing light to reflect and creating that metallic sheen highly sought after by breeders

Genetic Summary

Trait Gene Russian Blue Nebelung
Base color B BB Black BB Black
Dilution D dd dd
Coat length L LL ou Ll ll
Eyes Polygenic Selected green Selected green

Conclusion & Punnett Square

The Punnett square below illustrates a cross between two Russian Blues carrying the long-hair gene (Ll). It shows how the Nebelung variety (semi-longhair, ll) can reappear in a Russian Blue litter.

Theoretical litter ratios:

L
l
L
LL
Ll
l
Ll
ll
25% Homozygous short-haired Russian Blue (LL)
50% Heterozygous Russian Blue carrying long hair (Ll)
25% Semi-longhaired Nebelung (ll)

In conclusion, although the Russian Blue and the Nebelung are exhibited and judged under different coat-length criteria, they share an exceptionally close genetic heritage. Mastering these genetic principles enables breeders to preserve the elegant type and vivid coat qualities of both magnificent varieties.

Even when a breeding program focuses on the semi-long coat to develop the Nebelung, preserving the shorthair variety remains essential for maintaining genetic diversity, the original quality of the Russian Blue, and the overall balance of the breed.