The Tonkinese owes its characteristic intermediate/mink coat-pattern to the incomplete dominance of the genes which produce the solid coat-pattern of the Burmese (cb), and pointed coat-pattern of the Siamese (cs). Therefore, all progeny resulting from a mating of a Burmese with a Siamese will be Tonkinese and will have the typical Tonkinese coat-pattern (cbcs), but at this stage they may not necessarily have the desired type, eye colour or clarity of coat-pattern.

Mating Tonkinese with Tonkinese consistently produces 3 coat-patterns (with the associated eye-colour) resulting from the cb and cs pairing:

1. The intermediate, or mink, coat-pattern (cbcs), with the bluish-green eye colour

2. The solid coat-pattern (cb), with green/yellow eye-colour.

3. The pointed coat-pattern (cs), with clear blue eye-colour.

Irrespective of coat-pattern, the progeny of a Tonkinese x Tonkinese mating are Tonkinese and should be registered as such. The solid pattern should not be used in a Burmese breed programme; the pointed pattern should not be used in a Siamese breed programme.

A solid and pointed Tonkinese may not currently be shown under the GCCF, but if they have excellent Tonkinese 'type' they are valuable contributors to the Tonkinese breeding programme, particularly since a solid mated with a pointed can only produce the mink coat-pattern. Over several litters, the expected ratio of coat-patterns produced by a Tonkinese x Tonkinese mating will be 25% solid (cb), 50% mink (cbcs)  and 25% pointed (cs). From a solid/pointed x mink mating, the expected ratio of coat-patterns (over several litters) will be 50% mink coat-pattern and 50% solid/pointed coat-pattern.

Mating Tonkinese with either a Burmese or a Siamese is likely to cause divergence of the Tonkinese type therefore, since 1st January 2007, all progeny from the mating of a Tonkinese with any other breed (including Burmese and Siamese) are registered by the GCCF as 'No Recognised Breed'

It is necessary to permit the breeding of first generation Tonkinese (Burmese x Siamese) until such time as the Tonkinese gene pool is considered to be large enough, and diverse enough, to restrict it to Tonkinese only. However to progress the Tonkinese as a breed Tonkinese must be bred with Tonkinese. Therefore, since 1st January 1999, all progeny from first-cross matings (i.e. the mating of a Burmese with a Siamese) are placed on the GCCF Reference Register.

1. Cats selected for use in breeding programmes should be healthy and free from any known deleterious alleles or veterinary defects.

2. Tonkinese selected for showing and breeding should be as near the desired type as possible, having clearly defined Tonkinese coat-patterns and bluish/green or greenish/blue eye colour.

3. Tonkinese variants selected for use in the breeding programmes should be as near the desired Tonkinese type as possible and preferably have come from lines with the potential to produce excellent Tonkinese coat-pattern and eye-colour.

4. Burmese and Siamese, to be used in the breeding of first generation Tonkinese should be good examples of their breed and should have only Burmese or Siamese, respectively, in their pedigrees.

It is not acceptable to include Burmese-cross breeds (e.g. Bombay or Asian) or Siamese-cross breeds (e.g. Oriental or Balinese) in the Tonkinese breeding program because such breeds will introduce genes that are alien to the Tonkinese genotype.