The E Gene or Extension of Color in Rabbits

What is the color difference between these two rabbits?

Introduction

The photo above shows two rabbits, a jersey wooly and a holland lop. Each is much different in appearance when it comes to color. In fact both are genetically nearly the same except for one gene in their color. Care to guess what that gene might be? If you said the “E” or extension of color gene you would be correct.

The E gene is an odd gene. One allele which is dominant, yet when homozygous will block itself out. The most recessive gene creates an amazingly different looking rabbit.  This gene determines how far color extends on the hair shaft. It also has the ability to determine where on a rabbit particular colors will appear There are four possible alleles in this gene:

• “ES” – Steel
• “E” – Full extension of color
• “e” – Non extension of color
• “ej” – Japanese brindling gene

The “ES” – Steel Allele

The ES allele is the most dominate of all the E alleles. However, it has a strange genetic twist. First lets talk about what the Steel allele does to color. This gene works with the agouti gene. It will darken the middle band of color on the hair shaft. It also darkens the normally light agouti areas such as eye circles, belly and inside of the ears. However, it leaves a white guard hair which creates the “ticking” in the rabbit’s fur.

Normally when an allele is present in a homozygous form, thats what you see in the coat. This is not the case with this allele. When the ES allele is homozygous “ES ES” the allele does not show the steel ticking. Esentially this allele blocks itself out when present in a homozygous form. When it is heterozygous the steel ticking is visible or in the phenotype (ES E, ES e or ES ej). Breeds that have steel varieties include:

• Angoras (Except Giant and Jersey Wooly)
• Dutch
• Lop Breeds (Except American Fuzzy Lop)
• Netherland Dwarf

The “E” – Full Extension of Color

The “E” allele or normal extension of color allele is recessive to the “ES” allele or steel allele. It is dominate to both the e and ej alleles. It is probably the more common of all the alleles in this gene. Rabbits with this gene whether homozygous (E E) or heterozygous (E e or E ej) will have normal color.

The “e” – Non Extension of Color

The “e” allele changes how far out on the hair shaft the normal color will extend. The full color does not extend through the entire hair shaft. For example a black that gets the “e” allele either homozygous (e e) our heterozygous with the ej gene will become a tort. The black color only extends partially down the hair shaft but then becomes an orange color. Shorter hairs remain entirely black and longer hair shows more of the orange.

Breeds that have varieties using the “e” gene or tort varieties include:

• Angoras (Except Giant)
• Lop breeds
• Dutch
• English Spot
• Mini Rex
• Netherland Dwarf

The “ej” – Japanese spindling allele

The “ej” allele is the most recessive of the E genes. It must be homozygous (ej ej) for this allele to work. It is similar to the “e” alelle except instead of it affect an individual hair shaft it effects the location on a rabbit where color is or is not extended. The best example of this gene are Harlequins. Rather than color being non-extended on the hair shaft creating a tort, it non-extends in certain areas. This creates the harlequin pattern.

There are a few other breed with the ej allele present as well. This gene will create tri-coloring in rabbits. Compare an English Spot to a Rhinelander. The difference in color is the ej allele of the E gene.

Breeds with the ej present include:

• Harlequin
• Lop eared breeds (except American Fuzzy Lop)
• Mini Rex
• Rex
• Rhinelander

Breeding with the “E” Gene

As with any color or variety, care should be taken to ensure that your breedings result in showable rabbits. Full Extension (E) based varieties are very common. E allele dominant varieties can be bred with any other variety. Other varieties with the Steel or either of the recessive e and ej genes are far more rare.

Conclusion

The four alleles in the “E” gene make create some very unique coloring including steel tipping and harlequin patterns on rabbits. Care should be taken when breeding with anything other than the E allele as the other alleles can create unshowable animals.

Rob Usakowski
Three Little Ladies Rabbitry

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