Misc Interesting Genes

Other Intersting Genes

There are a number of interesting colour genes outside the major loci discusses elsewhere in the Genetics section. How well they are available for a mouse fancier, depends highly on one's location.

1. Silver si

The silver-gene causes silver ticking in the mouses coat. This means that the mouse's coat consists of different kinds of hairs: all white, all coloured, white tipped with colour and hairs with white and other colour in a striped manner. This gene is fully recessive. The amount of silvering and the depth of the colour, especially in the roots of the hairs varies quite a lot. Standardized silvered varieties are silver grey (silver Black), silver brown and silver fawn. Common to all the silvered varieties is, that the silvering develops with age. In the nest the mouse looks like non-silvered, but before two months of age the mouse becomes apparently silvered.

1.1. Ay/* - si/si

Silvered dominant yellow mice are called silver fawns, regardless of their eye colour. These mice tend to have rather light base of hair, although this isn't desired in the standards. The ticking manifests as mentioned above, but as the mouse gets old, the ticking becomes less obvious. It has not been studied how BB, Bb or bb background affects the colour. Other genes present affect the colour as they normally do.

1.2. A/* -- si/si

Silvered agouti mice have a lot of variation - some have lots of ticking, some look like regular agouti mice - they can be told apart form regular agouties by the light roots of hairs. However, this variety does not look like grey agouti, as the golden brown layer will not be affected by the silver gene. As the silver fawn, the silvered agouti looses silvering with age. For a fancier, this genotype would be silver brown.

1.3. at/* -- si/si

When tanned varieties have also the silvered gene, the result is silvered tan. (When foxed - silvered foxes). These mice have the top colour silvered as in non-tanned variety and silvered belly colour as well (silvered like in silver fawn).

1.4. a/a -- si/si

With a/a B/* si/si the mouse will be silver grey. These were formerly (in some standards still) recognized in three different shades - dark, medium and light. These shades mainly meant the colour of the roots of hairs. The belly of the silver grey mouse is slightly lighter than the top.

With a/a bc/* si/si you have the silver chocolate. The mouse should be rich golden brown in colour, with the ticking. In reality, the depth of the chocolate is reduced somewhat.

1.5. The Pearl mouse

This is somewhat arguable variety. The combination of a/a B/b si/si is an example where B does not fully dominate b and these mice are lighter in colour that a/a B/B si/si or a/a b/b si/si mice. The undercolour of these mice is almost pure white, leaving only the tips coloured dark. The effect is same with tanned varieties. Selecting for the lightest undercolour in silvered blacks and silvered chocolates should eventually lead to Pearls. However, this is rather difficult to breed

2. Leaden, ln

Under translation process.

3. Extension series, e

Under translation process.

4. Splashed, Spl

Under translation process.

5. Modifiers

Minor genes of major importance.

In genetics literature, modifiers are described as genes ?of minor importance?. For a fancy mouse breeder, they are quite important. While the major genes produce the desired colour, coat and markings as such, the modifiers produce the desired shade, quality of coat and the exact markings.

It is rather easy to get a, say, Blue mouse. Getting the right shade of blue on a Blue mouse is difficult. The same goes for practically all mouse colours, markings and coats. In order to get the exact shade, the desired amount and distribution of white on marked varieties and the desired length and/or curliness on coated varieties (as well as good short coat on a short hair mouse), the breeder will have to tackle with modifiers.

A good breeder needs to develop her eye for mice to be able to build the right modifiers to her strain of mice and to get rid of wrong ones. After all, the finer points of breeding involve exactly doing that. While a good understanding of genetics helps to get the right colours, it also helps in understanding the admittedly difficult and unstudied actions of modifying genes.

Studying pictures of good - and bad! - examples of all the different mouse varieties is a good thing. However, nothing beats first-hand experience of seeing mice live in shows, judged by a qualified, experienced standard class judge. Volunteering as a show secretary or assistant gives you a great opportunity of seeing show mice and hearing judges' opinions on them. Working at a pet show is another option, but only as an opportunity of seeing different kinds of mice. However, as pet shows are about good mouse husbandry and how healthy and tractable the mice are, these shows and pet show results do not tell anything about how good any given mouse is when it comes to the standards.