NOTE: While these are based on real life genetics of various creatures, primarily equines, this is a fictional fantasy group, and its rules will not align precisely with what Wikipedia, another ARPG, your teacher, your doctorate, or your grandmother might teach. Creative liberties have been taken!
Please also note that while it's encouraged, you do not have to follow group genetics rules if you don't want to! If you want that sparkledog, go for it!
Color genes are inherited from parents and provide the body with instructions on what colors fur, eyes, claws, etc. should be
ALL coats are made from a combination of two basic colors - Black and Red.
Some Base colors may appear very similar, but are controlled by totally different genes
The darkest version of Red may look nearly identical to the lightest version of Black, but many marking genes will interact with these two Base colors differently
Multiple shades can be present between markings and base coats. A Black-base coat creature can have a different shade of black for a "black stripes" marking, and another different shade of black for "black spots." Or, they may all be the same shade of black and blend together, it's up to you!
"Phenotype" refers to the visible appearance of a gene or creature (i.e. "Black" or "Black with Zebra Stripes")
"Genotype" is the genetic 'code' for determining base coats AND any additional markings, displayed in sets of two
ie. EE/Aa/Dn is a quicker way to say the creature has two "E" or black/eumelanin genes, one "A" or agouti gene, and one "D" or dun gene
Genotype is important because it tells you exactly what genes a creature can pass on to its offspring, including "hidden" genes
When writing genotype, usually, capital letters represent dominant genes, lowercase letters represent recessive genes, and "n" stands for null, meaning the gene does not affect color so it doesn't need a special letter. Dominant genes only need one of themselves to show, recessive genes need two of themselves to show, and n genes do not do anything.
"D", "WU", and "To" are all dominant genes because they start with a capital letter. "mlt" and "r" are recessive genes because they are in all lowercase.
The exception is ee/aa - E and A, the primary base coat modifiers, do not use null. e means there's no E gene present, instead of n as used for markings.
The "black body" gene is listed as "E" in a genotype. E stands for Eumelanin, which is the scientific term for black coat color. "A", the gene that distributes red and black in the coat, stands for "Agouti."
If a creature has an E gene, its body will be told to produce black coloration over the whole body. If the creature has an A gene, it will be told to produce red coloration over the whole body. If a creature has both E AND A, its body will produce black AND red coloration, making it a middle brown color.
There are several different types of "A" genes that can change where black and red appear on the base coat, creating a wide range of patterns
Genotypes for characters should always list some form of ee/aa, because these tell you what color the base coat is, but additional markings can be left out if they only contain n "null" genes (so you don't have to write Ee/Aa/nn/nn/nn/nn/nn/nn... )
Every gene (or "allele") has a specific place where it belongs on a DNA stip, just like a puzzle piece can only fit into one place in a puzzle. These individual spaces for specific types of genes are called "series." A creature can carry two genes from a series at a time - one of these is inherited from the father, and one is inherited from the mother.
Each gene will only fit in a specific series, but many different genes can be in that series
For example, the 'Agouti series' contains A, A+, and At, and these affect where red and black are allowed to show up on the base coat differently. A is a brown body with black legs, At leaves the entire body black except for the underbelly and face, which show a rich brown, A+ makes the entire creature brown except for its knees and the base of its feet.
Though there are multiple different genes in this series, a creature can only carry two of them in its genetic code. So they could, for example, be AA+ (or) A+A+ (but not) AA+ A+. They could also be aa for the series, and not carry any of these genes.
Genes (or "alleles") appear in sets of two, and offspring get one for each series from each parent.
A parent with Ee could give their child an E OR an e for that series, and it's a 50% chance to get either. If the other parent is ALSO Ee, the child could therefore end up being EE, Ee, or ee. See this video for help visualizing inheritance, as well as an overview on genetics in general!
When explaining genes in this guide, the _ symbol will be used to note that the gene in that slot of the genetic puzzle doesn't matter visually, because the gene listed is assumed to be dominant
ee/_ _ means that the genes in the "a section" can be anything in the "A series", and the creature will still look the same visually (in this case, red).
This is much shorter than writing out every possible combination, such as: "ee/aa (or) ee/Aa (or) ee/AA (or) ee/aa (or) ee/A+a (or) ee/A+A+ (or) ee/aa (or) ee/Ata (or) ee/AtAt (or) ee/A+At (or) ee/AA+ (or) ee/AAt (...)"
Some genes have a hierarchy that determines which ones show up, if they affect the same areas
For example: A+ is dominant over A and At, and if A+ is present, it will be the gene that shows visually on a creature even if it also carries A or At.
Some other genes are codominant, which means they both mix together, like red/white in certain flowers. If the flower has the red and white gene, it will appear pink because both colors are present.
The Base Coat genes, E and A series genes, will always appear underneath all other genes. Any marking genes, like spots or stripes, will go on top of the base coat.
Markings work like layers, one on top of the other. Black and red marking genes can be placed in any order, but the order should stay consistent - if you put "black stripes" over "red spots" on the legs, red spots shouldn't appear on TOP of black stripes anywhere else on the creatures.
White spotting genes will ALWAYS go on top of black and red markings and "cover them up", because white spotting actually removes pigment from the animal!