The Genetic

Before I show you the colors directly, I'm going to explain a little bit about genetics and the different alleles and loci.

The Alleles


A wild gerbil will always be Agouti. It is the basic color. The genetic code of a basic Agouti gerbil will be this :

  • A- C- D- E- P- Uw-

The letters represent what are called Alleles. Those in capital letters are what is called a Dominant Allele. This one will always have priority over a recessive allele in the writing order but also in the appearance of the gerbil. In general, we will not write the two dominant alleles in order to lighten the writing. When ignoring an allele, we will use a dash (-) or an asterix (*).

  • example :

    • AA CC DD EE PP UwUw is hard to write/read

    • A C D E P Uw is more refined

    • A- C D E- P Uw shows that we ignore the second allele of A and E.


A recessive allele will be written in lower case and cannot be expressed if it is alone. It must absolutely be double to be able to appear on the gerbil and we must therefore write it. If the gerbil has a dominant allele and a recessive allele, it will be said to be a carrier.

  • example :

    • aa C D E P Uw will be a Black gerbil.

    • Aa C D E P Uw will be an Agouti gerbil carrying non-agouti

The Loci

There are 7 loci in the gerbil. Each of them will influence the appearance of the coat and the final look of the gerbil.

  • A, the Agouti locus. Manages the intensity of the yellow color in the coat, as well as the black tip.

    • A, is going to be the normal color, with a white belly.

    • a, or not agouti, will order that the color is uniform over the whole body.

  • C, the Color locus, or Albino locus. This locus is normally used for the albino mutation (no color). As the cc does not (yet) exist in the gerbil, there is no real albino. It will control the accumulation of color in the hair of the gerbil.

    • C, the color will, by default, be uniform all over the body.

    • c[h], or Himalayan, is on the same chromosome as the albino. The gene controls the intensity of the color by fading it. In the presence of genes ee or pp, only one switch is needed to create an effect. Basically, it's the gene of Light. This gene is sensitive to temperature changes, and will darken if it is cooler (the extremities being colder than the body, they will be darker).

    • c[chm], or Chinchilla Medium, will fade the color while keeping the tips of the original color. Basically, it's the gene of Colorpoint ! This gene is sensitive to temperature changes, and will darken if it is cooler (the extremities being colder than the body, they will be darker).

  • D, the Dilute locus, manages the depth of the color.

    • D, will let the color express itself normally.

    • d, will distance the pigments in the hair, which will reduce the intensity of the color. Fewer black pigments in one place will give a gray tint instead, for example.

  • E, the Extension of Black locus. The gene will control the level of black in the hair. It is excessively sensitive to stains and fading.

    • E will define the extent of the black on the tip

    • e, or Extension of Yellow, will increase the amount of yellow in the hair at the expense of the black tip

    • e[f], or Fading, will do like e but drastically lightening the gerbil with age.

  • Uw, the Underwhite locus. It manages the intensity of the yellow color in the coat, as well as the black tip.

    • Uw, the original color.

    • uw, Underwhite or Cream, is a very rare gene that reduces the yellow for a cream while removing the black.

    • uw[d], or underwhite dense (formerly known as G, for Gray), will reduce the yellow in the coat for a cream, while slightly lightening the black. It will also pale the claws of solid gerbils for a brown and give a red reflection to the eyes.

  • P, the Pink-Eyed Dilution locus. It will control the number of black pigments in the eyes and the color of the hair.

    • P, or Non-Pink-Eyed, will leave the black eye.

    • p, or Pink-Eyed Dilution, will remove almost all the black pigments from the gerbil, slightly dilute the yellow and dilute the color of the eye with red.

  • Sp, le Locus Spotting

    • ++, or non-Spotted, will be a spotless gerbil. By default, it is not mentioned in the gerbil's genetic. A spotless gerbil can nevertheless carry a spot modifier and produce a fine line of Mottled if reproduced with a spotted gerbil. On a Self gerbil, the more white there is on the paws and chin, the larger the spots will be on the pups.

    • Sp, or Spotted, will define the extent of white spots on the gerbil and slightly dilute the original color. A spotted gerbil will always have the tip of the tail white. Whether the gerbil is Spotted, Pied, Mottled or even Dark Patched, it will be identified Sp.

The other Mutations

There are also other mutations that will influence certain elements of the appearance of the gerbil.

Steel : This gene will cause a very slight dilution going from the flank gradually to the stomach. We can also see some white hairs on the body despite the absence of spots, and also on the tail. These individuals also have white under the hind legs. This gene also reacts with Spotting, where there will be a lot of speckles, especially on the tail. When there are speckles, we say that the gerbil is Roan. All Roan are Steel, but not all Steel are Roan.

Dark Patched : This form of Spotting is very interesting. A Spotted gerbil will have its original color diluted. A Dark Patched gerbil is a spotted gerbil with a defined region of the original gerbil color. The shape and size may vary depending on the individual.

REX (Re[d]) : This mutation appeared in the Czech Republic in 2007. Although the individuals are called REX, the gene is in fact Rexoid.
It is a dominant gene, which requires a single REX parent for 50% of its young to be REX themselves. REX x REX mating may result in Double-REX (ReRe), which turns out to be a lethal combination. Double-REX do not survive more than three months, lose their hair and show signs of serious health problems (such as cataracts at 6 weeks). REX reproduction must therefore be done in a meticulous manner. Standard-haired babies born to a REX parent usually have a little longer coat than regular gerbils.

A REX gerbil will be identified Re[d].
A standard-haired gerbil born from a REX gerbil will be identified as Re[d]re.
A Double-REX gerbil will be identified ReRe.
We can recognize a REX gerbil from birth by its curly whiskers. The hair is very wavy in babies but will vary in intensity according to the moults in adulthood.