Or rather - what makes a mouse black?
Welcome to the weird and absolutely fascinating world of mouse colour genetics!
Being able to tell what kind of mice to mate in order to get mice of a given variety can get you nice mice. Knowing what the strange looking codes after a variety's name mean and knowing how to put that knowledge in practice will get you towards your goals faster. To truly understand breeding results and to figure out what matings would get you towards your goals the best before trying things out on live mice, makes your progress even faster and leaves you with less ?extra? mice to house, feed or place. Without knowledge on genetics, you wouldn't know if you were pursuing a variety that your breeding stock can't ever produce.
This said, let's get on with the actual business! Do note, that the language used is somewhat simplified. Few genes actually do affect the effect of another gene, but writing "gene z with gene Z" makes a much easier read.
The yellow (for a fancier: red) and black pigment are the basis for all mouse colours. Every colour and marked variety is the result of the distribution and intensity of these two basic pigments; yellow and black pigment are either full, diluted or absent. While brown pigment is a dilution of black and blue isn't actually a type of pigment at all, for a breeder both act as if they were basic pigments and are generally discussed that way. This is why articles on colour diluting genes will be discussing their effects on red, black, brown and blue.
Moving down the main loci in alphabetical order, each set of articles will be building on what has been discussed in the previous ones. So, while the a-locus articles touch briefly on diluted forms when discussing the different varieties with each of the a-locus genes, the later articles dealing with these diluting genes will be expanding on the subject and trying to explain what each diluting gene does and why a mouse with them looks the way it does. Furthermore, while "going down the dominance scale" in any given locus, the heterozygous forms with genes higher up on the dominance scale are not gone through again - these should be read from the earlier articles.
The mouse's coat consists of overhairs and underhairs. There are three types of overhairs (which form the ticking on agouti group colours and the "veil" on long hairs), while the underhairs is the rest of the coat.
The ABC of Genetics - Introduction to understanding genetics.
The Gene Chart - A chart of major colour, markings and coat variety loci, genes and examples of varieties. The chart can also be used as a site map for the genetics section. Start here.
A-locus - Ticked, tan or self? A-locus determines that. This locus includes a couple of brindling genes, too.
B-locus - Full colour or chocolate / brown dilution.
C-locus - The locus that gives us full colour or chinchillated / pointed / extreme diluted / albino (and even a version of Tricolor) and more. One of the most weird, headache-inducing and wonderful loci.
D-locus - Full colour or blue dilution.
P-locus - Full colour and black eyes or pink-eyed dilution - as well as interesting mottling genes.
Markings - Markings other than W-locus derived, like recessive white spotting s (Even, Broken), Rumpwhite, varitint waddler, sex-linked Brindle, Tortoiseshell, Roan, Merle.
Coats - Dominant and recessive curly coats, satin, longhair(s) and a bit on nude mice.
Miscellaneous - The rest: leaden, recessive yellow, pearl, silver-ticked, umbrous, varitint waddler, ruby eyes, modifiers
Glossary - Small dictionary of terms used.
For information on author and sources, see here.