The Marked Mouse

The Marked Mouse Below in the table are some of the genes that cause a mouse to be marked. These markings are as simple as a white spot on the head, and as complex as white smudges or brown stripes. To go to the official source for the information, click on the symbol for the gene. When available pictures accompany the different categories. Click on the picture for a larger view.
Symbol/Chr.	Picture		Information:
bt Chr. 15			Belted: Recessive. Homozygotes have a white belt around the back and a belly spot, both of which sometimes meet to create a belt around the mouse.
hs Chr. Un.			Headspot. This gene is highly affected by modifiers and may or may not appear on the offspring of two mice who both have head spots.
Rn Chr. 14			Roan: Dominant. Heterozygotes have white or partly pigmented hairs distributed throughout the coat. Homozygotes are lighter than heterozygotes and are viable and fertile.
Rw Chr. 5			Rumpwhite: Dominant. Heterozygotes have white hindlegs, tail, and posterior. Homozygotes die mid-pregnancy.
s Ednrb^s Chr. 14			Piebald: Recessive. Irregular white spotting on homozygotes. Homozygotes may develop megacolon.
si Chr. 10			Silvered: Recessive. Individual hairs on nonagouti silvers may be all white, all black, black with white tips, or white with gray or black bands. Silvering is very variable in appearance.
U Chr. Un.			Umbrous: Dominant. Causes a marked darkening in A/A mice, a mild darkening on A/a mice, and no effect whatsoever on a/a mice.

The Mo Locus ~ Chromosome X ~ Atp7a^Mo
Symbol	Photo		Description
Mo^br			Sex-Linked Brindle: Dominant. Heterozygous females have a mottled, patchy coat coloring, with curly whiskers. Patches with well defined edges very rarely cross the middorsal or midventral line. Males are almost completely colorless, except for small patches in the eye and ear region. They have curly whiskers and a wavy coat. Males usually die within 2 weeks of age. Those who live are fertile, and they have a behavioral abnormality consisting of a slight tremor, uncoordinated gait, and clasping of the hindfeet when held up by the tail. Homozygous females resemble Heterozygous males and die by two weeks of age.
Mo^to			Tortoiseshell: Heterozygous females have patchy mottled coat coloring, curly whiskers, and a silky lustrous coat. Hemizygous males die in vitro or are stillborn. .

The W Locus ~ Chromosome 5 ~ Kit^W
Symbol	Photo		Description
Dominant White Spotting. In general mice with this gene have areas of white on their coats, from simple spots to almost totally white. Homozygotes, with a few exceptions, are BEW and non-viable. Homozygotes with two different W genes are occasionally viable and usually BEW or BEW with some small pigment in the eye, ear, and sometimes rump and tail regions.
W			Variegated: Heterozygotes have variable amounts of white spotting, depending on the genetic background. Colored areas may be interspersed with white hairs to produce a roan-type of pattern. Homozygotes are BEW and die within a week of birth.
W^a			Ames Dominant Spotting. These mice resemble W mice except that they have a prominent blaze and more belly spotting. Homozygotes are anemic and die a few days after birth.
W^b			Ballantyne’s Dominant Spotting. These mice have white spotting and a slight dilution of color, similar to W^vmice with more dilution & more spotting. Homozygotes may survive to maturity, if so they are BEW, anemic, and sterile.
W^bd			Banded. Closely related to rumpwhite mice. Homozygotes are BEW with slight pigmentation on the ears and snout, and occasionally on the rump and tail region. They are viable and fertile but slightly anemic. Heterozygotes have a broad band of white in the trunk region.
W^sh			Sash. Heterozygotes have a broad white sash around the body in the lumbar region. Homozygotes are BEW, fully fertile, and viable.
W^v			Viable Dominant Spotting. – Heterozygotes have a variable amount of spotting and also a slight dilution effect on the colored hairs. Homozygotes are BEW and anemic. Those who survive to maturity are possibly sterile and could have hearing problems.
Miscellania. The genes listed below are the remaining genes which affect the color of a mouse. Some of these genes may only be found in a laboratory and are offered here as simple curiosities. Some however, are definitely found in the mouse fancy.
Symbol	Chr.	Information
e Mc1r^e	8	Recessive Yellow: Homozygotes are a clear yellow with black eyes. Slight sootiness on the back may occur before weaning but disappears with successive molts. Viability, fertility, body weight, and tumor incidence are normal. In combination with either piebald or belted, e decreases the amount of white spotting.
ln	1	Blue. Identical in phenotype to the blue dilution d.
pe Ap3b1^pe	13	Pearl: Homozygotes have a smaller amount of pigment in the eyes at birth, but eye color cannot be distinguished from that of normal in adults. The yellow and black pigments of the coat are diluted. Viability until maturity is good, but females have a tendency to die during pregnancy/lactation, and the survivors are poor mothers.
Crm	X	Cream: Hemizygous males and homozygous females are pale yellow. This color is expressed even in the unpigmented areas of mice with white spotting and in albino mice. It causes fluorescence of the coat in UV light, which produces a clear mosaic pattern of fluorescent and non-fluorescent areas in the coat.
bf	5	Buff: Non-agouti buff mice appear to be khaki colored. Eye color is not affected.

Information:

Belted: Recessive. Homozygotes have a white belt around the back and a belly spot, both of which sometimes meet to create a belt around the mouse.

Headspot. This gene is highly affected by modifiers and may or may not appear on the offspring of two mice who both have head spots.

Roan: Dominant. Heterozygotes have white or partly pigmented hairs distributed throughout the coat. Homozygotes are lighter than heterozygotes and are viable and fertile.

Rumpwhite: Dominant. Heterozygotes have white hindlegs, tail, and posterior. Homozygotes die mid-pregnancy.

Piebald: Recessive. Irregular white spotting on homozygotes. Homozygotes may develop megacolon.

Silvered: Recessive. Individual hairs on nonagouti silvers may be all white, all black, black with white tips, or white with gray or black bands. Silvering is very variable in appearance.

Umbrous: Dominant. Causes a marked darkening in A/A mice, a mild darkening on A/a mice, and no effect whatsoever on a/a mice.

Tortoiseshell: Heterozygous females have patchy mottled coat coloring, curly whiskers, and a silky lustrous coat. Hemizygous males die in vitro or are stillborn. .

Variegated: Heterozygotes have variable amounts of white spotting, depending on the genetic background. Colored areas may be interspersed with white hairs to produce a roan-type of pattern. Homozygotes are BEW and die within a week of birth.