Extension Locus - E
The E Locus has four different alleles in it: ‘Eˢ’, ‘E’, 'eʲ', and ‘e’. ‘Eˢ' is the most dominant, ‘E’ is the next most dominant, then 'e(j)', and finally ‘e’ is the most recessive.
* Some people claim a fifth, most dominant allele, of Eᵈ, which is said to be a dominant version of self. However, it is likely this has just been hidden steels with A_ Eˢe genotype, which generally appear self (Fontanesi et al., 2006). That said, other species, such as dogs, do have a dominant version of self, so it is possible this allele exists.
Gene involved: MC1R (melanocortin 1 receptor) gene
STEEL
This allele causes the rabbit to have lighter colored tipped guard hairs in an otherwise dark coat.
The ‘Eˢ’ allele is the Steel allele. All Steel rabbits must have at least one of these alleles. If they have two of these alleles, then they are homozygous (Meaning it is “pure” for that allele, so that it cannot produce anything recessive to it no mater what it is bred to.) for Steel. Steel can get very complicated, so I will be eventually writing an article just on it! The following are examples of varieties that have the Steel allele:
Gold-Tipped Steel (Black, Blue, Chocolate, Lilac), Silver-Tipped Steel (Black, Blue, Chocolate, Lilac, Sable, Smoke Pearl)
Steel can carry Extension, Japanese, and Non-Extension.
Black-Tipped Gold Steel
This specific genotype of A_ EsE is what makes proper, showable steel colors.
A_ B_ C_ D_ EˢE enen
Steeled Silver Marten
Not showable in any breed, but they look neat!
Genotype:
aᵗ_ B_ cchd_ D_ EˢE enen
Photo credit: Dichrome Rabbitry
Steeled Californian
It is difficult to see the steel coloration on a Californian! I know he is steel because he has produced steel with non-steel. The steeled silver marten kit is his!
Genotype:
A_ B_ cʰ D_ EˢE enen
Photo credit: Dichrome Rabbitry
Self Steel
These combinations make a steel appear like a normal self rabbit with little to no ticking.
Possible Genotypes:
aa B_ C_ D_ Eˢ_ enen
A_ B_ C_ D_ Eˢe enen
A_ B_ C_ D_ EˢEs enen
Photo credit
Steeled Harlequin
The steel tipping only occurs where the harlequin would have orange or white stripes, whereas the black stripes remain solid black.
FULL EXTENSION
This is the allele that is the "normal" and is what a wild rabbit (Chestnut color) would have (Fontanesi 2021).
The 'E' allele is the Extension allele. All Extension animals must have at least one of these alleles. If they have two of these alleles, then they are homozygous for Extension. The following are examples of varieties that varieties have the Extension allele:
Black, Blue, Chocolate, Lilac, Castor, Chestnut, Copper, Sandy, Gray, Chinchilla (Black, Blue, Chocolate, Lilac, Seal, Sable, Smoke Pearl), Opal, Lynx, Chocolate Chestnut, Cinnamon, Himalayan (Black, Blue, Chocolate, Lilac), Tan ((Black, Blue, Chocolate, Lilac), Otter (Black, Blue, Chocolate, Lilac), Silver Marten (Black, Blue, Chocolate, Lilac), Sable Marten, Smoke Pearl Marten, Sable, Siamese Sable, Smoke Pearl, Seal.
Extension can carry Japanese and Non-Extension.
Silver Marten
aᵗ_ B_ cᶜʰᵈ_ D_ E_ Enen
Photo credit: Dichrome Rabbitry
JAPANESE
This allele causes the orange and the color (black, blue, chocolate, or lilac) to separate onto different hairs, often in banded or checkered patterns, though they may also be brindled (Fontanesi 2021).
The ‘e(j)’ allele is the Japanese gene. All Harlequin or Tricolor animals must have at least one of these alleles. If they have two of these alleles, then they are homozygous for Japanese. The following are examples of varieties that have the Japanese allele:
Tricolor (Black/Orange, Blue/Fawn, Chocolate/Orange, Lilac/Fawn), Japanese Harlequin (Black, Blue, Chocolate, Lilac), Magpie Harlequin (Black, Blue, Chocolate, Lilac), Brindle (Black, Blue, Chocolate, Lilac), Magpie Brindle (Black, Blue, Chocolate, Lilac).
Japanese can carry Non-Extension. If Harlequin or Tricolor rabbits carry Non-Extension and are Self-based (aa), they may have tortoise shading in their orange or sable point shading in their white.
Harlequin (lilac magpie)
A_ bb cᶜʰᵈ_ dd eʲ_ enen
Photo credit: Dichrome Rabbitry
Harlequin
A_ B_ C_ D_ eʲ_ ene
Harlequin is the solid version of tricolor. Tricolor is the broken version of harlequin.
Tricolor: ej_ (plus broken Enen)
Japanese (ej) is incompletely recessive to full extension (E). In agouti and tan pattern rabbits that are Eej, you will see harlequin/tricolor pattern in the orange or white portions of the rabbit.
Harlequinized Silver Marten
Note the darker half of the face.
aᵗ_ B_ cᶜʰᵈ_ D_ Eeʲ enen
Photo credit: Angela Swain
Harlequinized Silver Marten
Note the darker patches on the belly.
aᵗ_ B_ cᶜʰᵈ_ D_ Eeʲ enen
Photo credit: Angela Swain
Harlequinized Castor (Chestnut)
Note the darker patches on the face.
A_ B_ C_ D_ Eeʲ enen
Photo credit: Pine Grove Farm
Harlequinized Castor (Chestnut)
Note the darker patches on the belly.
A_ B_ C_ D_ Eeʲ enen
Photo credit: Pine Grove Farm
NON-EXTENSION
This allele reduces the amount of color (black, blue, chocolate, lilac, seal, sable, or smoke pearl) that is found on the coat (Fontanesi 2021).
The ‘e’ allele is the Non-Extension allele. All Non-Extension rabbits must have two of these alleles.
The following are examples of varieties that have the Non-Extension gene:
Red, Orange, Fawn, Cream., Frosted Pearl, Ermine, Tortoise (Black, Blue, Chocolate, Lilac), Tortoise Otter (Black, Blue Chocolate, Otter), Sable Point, Fox (Black, Blue, Chocolate, Lilac),
Frosted Pearl/Frosty
A_ B_ cᶜʰᵈ_ D_ ee enen