Genetics in general
Genetics is a research area in which people study inheritable characteristics, the consequences of these characteristics for the organism (in our case the chinchilla) and how these characteristics are passed on to the next generation(s). Two terms that are commonly used in articles about genetics are genotype and phenotype. The genotype is the genetic code of an organism, while the phenotype describes the appearance of the organism. For instance, a beige chinchilla has the genotype Pwpw (code will be explained later) and the phenotype beige. When limiting the genetics to the fur colour of chinchillas, you can say that the phenotype is more or less equal to the colour of the animal.
Another commonly used term is ‘mutation’. A mutation is a change in the genetic material of an organism that causes the change of a certain characteristic (e.g. the colour of the fur). A mutation can be passed on to the next generation(s), but this is not always the case. Every gene is present in two copies on the DNA of a chinchilla and it is highly unlikely that a new mutation occurs at exactly the same place in both copies. In most cases, one of the genes will be mutated, whereas the other is not. An animal like this is called heterozygous for this characteristic. If the animal carries the mutation on both copies it is called homozygous and if it does not carry the mutation it is called a ‘wild type’.
Mutations can be dominant or recessive. Dominant mutations result in a change in the phenotype in a heterozygous animal. They change the phenotype in the presence of a wild type copy and therefore overrule this copy. Dominant chinchilla fur colours are white, beige, ebony and velvet. Recessive mutations only result in a change in phenotype in the homozygous form. The presence of a wild type copy in the heterozygous form overrules the mutated copy. Such an animal is called carrier for a mutation. Recessive chinchilla fur colours are (African) violet, sapphire, (German) violet, charcoal and recessive beige.
The way to describe a mutation in the genotype of an organism is different for dominant and recessive mutations. For dominant mutations the mutated copy is indicated by a capital letter and the wild type copy by a lower-case letter, while for recessive mutations the mutated copy is indicated by a lower-case letter and the wild type copy by a capital letter. Looking again at the previous example beige: Pw is the indication for the dominant mutated copy, while pw describes the wild type copy.
Chinchilla colour mutations
These days you can find a large number of different chinchilla colours, but they are based on a small number of mutations. The large variation is the result of different combinations of these mutations. Most of the common chinchilla colours are based on 8 mutations. The table below lists these mutations and their genetic codes. For beige and ebony, the homozygous form is (in most cases) clearly different from the heterozygous form. For white and velvet the homozygous form is lethal, which is why these are not listed in the table.
For African violet, sapphire and charcoal, the heterozygous form has the phenotype of a wild type (or standard) animal and these are therefore not indicated.
I have been able to find a number of different systems to describe chinchilla genetic codes, but the two most commonly used ones are obtained from a journal called ‘Die Deutsche Pelztier Züchter’ (column DPZ) and the ‘Mutation Chinchilla Breeders Association’ (column MCBA). However, for some mutations I have not been able to find their code, so I have introduced one myself and marked them with *. The table also lists whether a mutation is dominant or recessive.
Using the DPZ code to write down the genetic code of a wild type (standard) chinchilla gives: blbl, ww, pwpw, ee, BB, SS, VV, GG.
Some people consider the ebony mutation a recessive mutation, because the animal becomes darker in the homozygous form. I personally don’t agree with that, since a recessive mutation should not result in the visible phenotype that most hetero ebony chinchillas have. In a way, ebony and beige work in similar ways, in that the colour of a heterozygous animal is different from the wild type, but the difference is more pronounced in a homozygous animal.
Apart from the mutations discussed above, other chinchilla colour mutations have been reported: Sullivan beige (recessive), albino, misty, goldbar, recessive white.
Most of the other commonly found colours are combinations of the colours described above. Some examples:
- brown velvet: black velvet / beige (Blbl, Pwpw)
- brown ebony: homozygous ebony / beige (EE, Pwpw)
- rosé/pink-white: white / beige (Ww, Pwpw)
Unfortunately, the naming of a colour is not always consistent, especially when you compare the names that are used in the USA, UK, Germany and the Netherlands. For instance, dark pastel was originally used for an animal that had the charcoal and beige (ccPwpw) mutations, while light pastel was an animal that had the charcoal and blond mutations (ccPwPw). These days, pastel is commonly used for animals that have the ebony and beige mutations (EePwpw). Light and dark now refer to the colour variation that is common in heterozygous ebony chinchillas. A second example is ‘tan’. In some cases this is used for brown ebony (see above) chinchillas, while other people use this to describe a heterozygous ebony / beige chinchilla.