Finding examples of gene combinations can be challenging - below are some examples showing phenotype/genotype across different traits.
The color terms I use don't always match what AFRMA (or other clubs) recognize, mostly because what they recognize are limited to certain standards and don't always inform on the genotype of the animal. For those of us who aren't hard-core show rat people, it's a lot more valuable to be able to look at a rat and understand what genes are at work are making it look the way it does. I've attempted to include commonly accepted genotype codes when possible.
[this post is in progress, I'm hoping to replace the photos with better quality ones!]
Body Type
Specific genes that alter the size/shape/form of a rat, regardless of what their fur looks like.
"Show type" rats are selectively bred for particular traits closest to a defined standard - these can be things like overall body shape, head shape, the way the tail tapers from the body, etc.
Standard - normal size, normal ears, normal tail, etc. |  |
Dumbo - Ears placed low to the sides of the head. Recessive [du/du] |  |
Dwarf - Adults are only about 1/3rd the size of standard adults. Recessive [] | |
Tailless / Manx - Partial or missing tail. "Complicated" Recessive [multiple genes] | |
Coat Types
These genes impact the texture, length, or structure of the hairs. Are the hairs straight or curly? Are they "hollow" inside like a polar bear's? Do the hair follicles function normally? Coat types CAN impact color, but are more to do with hair structure than the pigments present.
Standard |  |
Rex Dominant, heterozygous: [Re/re] | |
Double Rex Dominant, homozygous: [Re/Re] Double rex can look practically hairless, or have thin, patchy/fuzzy hair. |  |
Hairless Recessive [hr/hr] |  |
Velveteen Dominant [V?/*] | |
Silvermane / D'Argent - Ends of the hair shafts are hollow/translucent, causing a silvering effect that matures in the adult coat. Dominant [Sm/*] (See what silvermane looks like on different colors here!) |  |
Harley - Longer, wispy/thin hair. Recessive [l/l] (lowercase Ls) | |
Patchwork / Werewolf Recessive [] | |
Satin Recessive [sa/sa?] (not very common in US outside of show breeders) | |
Patterns
Patterns and markings are areas where pigments are inhibited (or enhanced) in particular areas. Most patterns and markings are in the form of white (no pigment) patches. Very often there are multiple markings that all arise from selectively breeding one gene but for different presentation. The "Hooded" gene is responsible for hooded rats, berkshire rats, irish rats, whiteside rats, etc. Patterns are separate from whatever "color" a rat is at its base. For example, a cinnamon rat can also be albino - which would cover up all evidence of the underlying color.
Standard (Self) - No markings or patterns at all. | |
Hooded - Highly variable and VERY common / widely distributed. Dominant: [H/*] | |
> Berkshire | |
> Irish | |
> Capped | |
> Blaze | |
> Downunder | |
> Whiteside | |
Albino Recessive [c/c] |  |
Himalayan Recessive [c^h/c] (pictured is a blue himalayan) |  |
Siamese Recessive [c^h/c^h] | |
Marten | |
Black Eyed Dominant [Be/*] With this gene, eyes that would normally be pink/ruby stay black. It however is not expressed in albino (eyes are still pink even with this gene). The rat pictured is a black-eyed himalayan and would otherwise have pink eyes. |  |
Roan / Husky | |
Merle | |
Marble / Spotted Tabby | |
Dalmatian Homozygous Lethal | |
Colors
Each gene impacting color will look different depending on whether it's acting on a banded (agouti) hair or solid (black) hair - and generally people will call colors different names depending on which A locus base (agouti or black) they're added to.
Naming colors in rats is a mess. It varies depending on what country you're in, what part of what country, what breeder you're talking to, etc... if you're confused, don't worry, everyone calls everything something different.
| Agouti (A/A or A/a) Base | Black (a/a) Base |
No other presenting colors May carry mink, blue, ruby eye, etc. | Agouti   | Black   |
Add mink [m/m] | Cinnamon  | Mink  |
Add blue [g/g] | Blue Agouti  | Blue |
Add ruby eye [r/r] | Fawn | Beige |
Add pink eye [p/p] | Silver Fawn | Champagne |
Add mink + blue [m/m g/g] | Lynx | Platinum, (Lilac)  |
Add ruby eye + mink [r/r m/m] | | Havana? |
Add blue + ruby eye [g/g r/r] | | |
Add blue + pink eye [g/g p/p] | | Silver |
Add Russian blue [d/d] | | |
Add chocolate (not very common in US outside of show breeders) | | |