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Genetics Information

Colours and Combinations: G Locus

The G Locus

The G locus, also known as the Grey Locus, is responsible for the dilution of the black pigment (eumelanin) to a blue-grey. The wildtype of this Locus is dominant and represented by “G”. Each strand of hair contains black pigment. The recessive mutation is represented by “g” and causes the pigment in each strand of hair to be diluted to a blue-grey. This causes the rat to be a grey-blue colour that can vary from dark (blue) to very light (powder blue). When the rat has no other mutations on the other loci and is Agouti based and is dominant on this locus, the colour is known as Agouti. When it is agouti based and has a recessive allele this locus, it is known as Slate. When the rat is black based with a dominant allele on this locus, it is known as Black. When it has a recessive allele on this locus it is known as Blue.

Alleles on the G locus are as follows:

G- Black
g- Blue

GG and Gg animals will have normal eumelanin, while gg animals will have diluted eumelanin.

CLR Fauna
Blue Berkshire Standard Ear


Mischief Managed Rattery Litter
Left to right: Black, Agouti, Slate

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