Markings, other than W-series.

This is a wide group, with genes from different loci. There are also two "types" of markings genes discussed; ones which will cause patterns of white and colour (which depends on other genes present) and ones which cause patterns of coloured stripes or similar without one of the colour being white.

1. Recessive white spotting s

The recessive white spotting gene s is responsible for mouse varieties called Even and Broken marked. The gene is called "piebald" and it is associated with so called "k" complex of modifiers. As stated, this gene is responsible for two varieties, maybe even the Dutch (although this is debatable) and the main difference is what kind of spotting (evenly or unevenly placed) is being selectively bred towards. The main effect of this gene is larger, clear cut coloured spots / patches on a white background.

a/a B/* s/s & a/a b/b s/s pic: Arttu Väisälä

Black broken, a/a B/* s/s pic: Anniina Tuura

Black dutch, a/a B/* s/s (?) pic: Anniina Tuura

These spotted varieties aren't very easy to breed, although spotted mice are rather easily found in pet shops around the world. The diffuculties are brought in because the gene and the markings it produces are greatly affected by the modifiers. Without the presence of right modifiers, a ss mouse may have only a few white spots on the belly, feet and forehead. In the other extreme end - these mice may be almost totally unpigmented! All in all, the mouse's belly has more white than the top side. As the mouse becomes less pigmented, the last areas to lose pigmentation are the eyes, cheeks, ears and haunches.

The s-gene has been reported of being associated with megacolon and there have been reports of some 10% in some laboratory strains of s/s mice having this condition.

1.1. The Dutch mouse

It is argued, that the Dutch markings in mice would actually not be caused by the recessive white spotting gene, but some kind of gene of its own. This is backed up with the notion that if you cross Dutch with self, you will return to (poor) Dutch after only one intermediate generation.

2. Rumpwhite R^w

Rumpwhite is caused by a lethal dominant gene R^w, thus all Rumpwhites are heterozygous and breeding Rumpwhite to Rumpwhite will cause 25% smaller than average litters. The gene being dominant, it is fairly easy to introduce this marking into new colours. However, these mice usually have only white tail and small patch of white in the rump. It takes quite a lot of selective breeding to establish the markings required by standards. Therefore, Rumpwhite isn't one of the easiest varieties to breed and the breeder does need quite a lot of patience and a number of breeding stock.

2.1. Interaction between R^w and other marked genes

When R^w is combined with piebald (recessive white spotting), the mice have pigmented hairs on their heads and shoulders, but little elsewhere. With belted (bt/bt) the mice resemble Rumpwhite, but with quite uneven demarcation lines. With Banded (W^sh) to Rumpwhite matings there have been Capped-like mice, as well as mice who resemble the rat variety Bareback.

3. Brindle (UK) Mo^br

The effect of this gene is sex-related. The Brindle males are almost white with sooty tips (they look like siameses) and the coat is curly. This gene is usually lethal in males, and they usually die at 10 - 14 days of age. Sometimes, some will survive and live to be adults. However, these mice suffer form neurological conditions, which makes them "wobble" and their hind legs to clasp each others when held by the tail. If a Brindle male is mated to Brindle female, the resulting heterozygous females resemble the homozygous males.

In females, this gene causes brindling pattern in the coat. Some are lighter, some darker and they tend to get darker with age. The pattern can be selectively bred to show better brindling. There have been reports of also females being "wobblers" in Brindle.

4. Belted bt

Belted is an older variety than the Banded and originated from a lab in 1940's. This recessive gene causes a thin belt around the mouse's waist when homozygous. At the arrival of the Banded mouse, the Belted was becoming rare and there was some confusion among the mouse fanciers. Nowadays, Belted isn't fully standardized anywhere to my knowledge. However, some Belted mice appear every now and then. If you have mated two self mice together and get mice with a thin belt in the litter, you most probably have a Belted in your hands!

(Just a slight note: some genetically banded mice may show only a small white belly spot or even just a couple of white hairs and when mated to a self produce clearly banded mice!)