E-Locus (Extension of Color)

Genes: E Es e ej

The E locus is the second-most complicated locus (after the C Locus). The E locus manages the quality, quantity, and distribution of the black pigment in a rabbit's coat. 'E' stands for extension (or non-extension) of the black pigment on the fur shaft. Remember that “black” can be displayed as other colors depending on the other loci modifiers so black, blue, chocolate, lilac). The E/e gene controls whether the basic color on the rabbit (black, blue, chocolate, or lilac) is extended all the way to the end of the hair shaft or whether the basic color stops, and another finishes the hair shaft (such as the orange color on the back of a black tortoiseshell aka black tort).
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When a rabbit has full extension (E), it tends to look the same color all over, such as with a blue rabbit. When there is non-extension (e) such as with a black tort, the rabbit takes on a shaded look since the shorter hairs on the belly, guard hairs, feet and muzzle get only the basic color (they are not long enough to get the other color that finishes off the longer hairs). Some C genes can also give a shaded look for a different reason (check out the sable gene, for example). That all sounds simple enough, but there are some complications (of course there are, right?).

Besides E (extension) and e (non-extension), there are two more variants in the E locus. One is Es (steel), which carries a surprising twist! Typically, the gene that is found in nature (in this case, E), is the most dominant gene. But in the case of the E locus, Es- steel is dominant over E- full extension.
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The E locus genes also share partial dominance, which can sometimes cause the second E gene of a heterogyzous (not identical) pair to show through (such as in the case of a harlequinized chestnut which would be Eej). The E genes are also linked to the A genes, and many of the E genes won’t show unless they are on an agouti coat (A_).

Ed Gene

There is some belief that there is another gene called Ed (Extension Dark or Extension Dominant). There are other beliefs that say there is no Ed gene, and that the expression of it is a double Es gene. Since this is still a controversial idea, I am leaving the existence (or non-existence) of the Ed gene out of this lesson.

Es: STEEL

• Most dominant gene, dominant over E, ej, and e.
• Common varieties of Es: gold-tipped steel in a variety of colors, silver-tipped steel in a variety of colors, super steel (EsEs)
• Possible gene combinations of the E locus with Es as the dominant gene: EsEs, EsE, Eej, Ee

Gold tipped steel Flemish Giant junior (Es_)

The steel gene (Es) covers the middle band of color in Agouti coats (A_) by carrying the dark pigment mostly up the hair shaft and leaves ticking (a little light color at the tip of the guard hairs). On an agouti rabbit (A_), it will also remove the white belly. Es has incomplete dominance over the other genes in the E locus. It over-produces black pigment on the hair shaft, overwhelming and invading the normal pattern of color. Despite this incomplete dominance, Es is listed first (EsE) since it overpowers the other E locus genes. The steel gene can be troublesome since it seems able to hide itself if the rabbit is not an Agouti (A_). Since tan (at_) and self (aa) rabbits already have single-colored hair shafts, there is no light color at the end for the steel gene to leave. To identify Agouti (A_) rabbits that expresses steel, look for the rabbit’s under-color to extend all the way up the hair shaft, wiping out the ring.
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For further information about the steel gene, visit: https://www.raising-rabbits.com/steel-rabbit-genetics.html

E: FULL EXTENSION

• ​Recessive to Es, dominant over ej and e.
• Common varieties of E: Chestnut, opal, black, blue, chocolate, black otter
• Possible gene combinations of the E locus with Es as the dominant gene: EE, Eej, Ee

Broken black Rex junior (E_)

The E gene allows dark brown/black pigment to be fully expressed and allows the banding and colors to show through naturally. E is the original dominant gene for the E locus. Most rabbits are EE.

ej: JAPANESE HARLEQUIN (ALSO CALLED HARLEQUIN)

• Recessive to Es, E. Dominant over e.
• Common varieties of ej: all four colors of harlequin and tri (broken harlequin): black/orange, blue/fawn, orange/chocolate, fawn/lilac, and magpie (cchd_ harlequin or cchl_ harlequin)
• Possible gene combinations of the E locus with ej as the dominant gene: ejej, eje

​The Japanese Harlequin gene (also known as just harlequin and sometimes shortened to “harli”) produces a brindled pattern by segregating the dark brown and yellow pigments. It keeps the bands of color in separate areas rather than on one hair shaft. This gene causes some areas to over produce black pigmentation, and some areas to under produce black pigmentation.

Blue/fawn harlequin Rex (ej_)

Black/Orange Harlequin New Zealand cross (ej_)

Black/orange tri-colored mini lop (ej_)

Black/orange tri-colored Rex (ej_)

This is an interesting gene in that if you add the broken gene (more on this later- this is a separate gene on its own locus), then the rabbit becomes a tri-colored rabbit (or tri) and the pattern is broken up differently (dark spots on a lighter field rather then stripes or splotches).
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To make things further interesting, this gene can be expressed partially with only one copy on agouti (A_) and tan (at_) rabbits with E in the dominant spot. It would be hidden on a self rabbit (aa). Typical signs of this expression are spotting along the edges and/or insides of the ears, around the eyes, and faint banding on the cream/white belly of the rabbit.

e: NON-EXTENSION

• Most recessive gene, recessive to Es, E, and ej.
• Common varieties of e: red, fawn, orange, cream, ermine, tort, sallander
• Possible gene combinations of the E locus with e as the dominant gene: ee

e (non-extension) is the most recessive gene in the E locus, and can only be dominant with a copy of itself (ee). e removes most dark brown piment and blocks extension of black pigment. Only the yellow/red pigment shows so you get colors like tort, orange, red, and cream. When its effect is imperfect because of other modifiers, you can sometimes get “smut” or “soot” on the rabbit. The darker pigments barely extend up the hair shaft and are quickly replaced by another color. The result is that the rabbit’s coat appears to be shaded, despite there not being a cchl gene. This is because the darker color at the base of the fur is only showing up on the parts of the body with shorter hair- ears, nose, paws, tail, flank, etc. The hair is not long enough in those places to show the other colors that appear on the longer hair shafts.

Red Rex buck (ee)

Red Rex (ee)

Blue fawn Rex bands (ee)

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On to the "En" Gene...