Eva's Rat Colours Page - Complementation Test

Complementation test:

Sometimes you need to testmate certain colours in order to get know how they are inherited. If we want to know of the blue colours are determined by alleles at one locus or two different loci we need to make a complemention test. The theory is that

1. you cross two animals that are homozygous for the same character you are looking at (here blue) you will only get that character in the litter (all blue babies).
   Example: German Blue (aadd)*German Blue (aadd) gives all German Blue babies (aadd).

2. you cross two animals that each are homozygous for one of the two characters you are looking at (here two different blues) you will not get any of those characters in the litter (all black babies).
   Example: English Blue (aagg)*German Blue (aadd) gives all Black babies (aaDdGg).

3. you cross two animals that each are homozygous for one of the two characters you are looking at, but the genes are alleles (here albino and siamese) you will not get any of those characters in the litter, but you may get some kind of combination of the two involved phenotypes (all himalayans).
   Example: Albino (cc)*Siamese (c^hc^h) gives all Himalayan babies (c^hc).

Three different blue rat colours: Today we have three different blue colours on the rat in Sweden.
The three blue colour are:

1. German Blue, a dark blue colour imported from Germany in 1995. This colour looks and acts just like aadd in all other species, so I call it aadd. I have had this gene in my lines since 1995 and done many test matings with it.

2. The colour English Blue, was imported from England in 1995, where it is considered to be aadd. This colour does not at all look like aadd in other species and I call it aagg. In the US they have another blue colour, that they call just "Blue" and this colour may be the same genotype as our English Blue, but this has not yet been test mated, but it looks very much like our English Blue! The US colour Blue is also denoted aagg. Remember that Blue and English Blue are not complementation test mated with each other yet (as far as I know).

3. The colour Russian Blue was imported to Sweden from the US in 1998 as Russian Blue. In the US it is considered to be aadd (I do not agree with this proposed genotype since if you put a Russian Blue beside a German Blue the German Blue looks most like aadd in other species. With German Blue I have produced silver, lilac, blue agouti and many many other colours, which I have been told is not possible with Russian Blue. I have not tried this myself, and since German Blue is a prettier colour than Russian Blue I may never do so.

Testmating English Blue and German Blue

These colours are quite different in appearance, so when an English Blue rat and a German Blue rat was mated (somewhere around 1995 in Sweden) and produced only Black babies no-one was the least surpriced.

Testmating German Blue and Russian Blue

German Blue and "Russian Blue" was testmated in July 1999, by me and a friend here in Stockholm, Sweden. Since they produced a whole litter of blacks, plus a litter of only black and beige, this proves that these "blue genes" are situated on different loci.

When I saw my first Russian Blue I though it was a badly colour bred German Blue, and therefore I was pretty convinced the test mating between Russian Blue and German Blue would produce blue babies... But alas that was not the case!

Testmating English Blue and Russian Blue

I have recently been told by a Swedish breeder called Linda Sebek that this test mating have been done, if I remember correctly this was in the Netherlands. All that was produced was black babies.

Result

These three testmatings can only be interpreted as that there are three different known genes in the rat fancy that expresses the recessive trait "blue colour".
Eva's Rat Colours Page - 3 different blue colours - how do you know the difference?

All photos by Eva Johansson.
Last update: 13th of February 2006.