Genetics basics:
Every living creature has DNA, made up of several chromosomes. Each chromosome has alleles, and each allele carries genes that determine the expression of various traits. While real-world genetics encompasses everything from gender and pelt color to health and temperament, here at Nezumi's Children we're only interested in a handful of genes.
Every single rat that you color has a genotype, or genetic code that defines what the rat looks like. It's important to keep track of the genotype, as some genes may be recessive or covered up by other genes; you can't see them on the rat itself, but they might show up in its offspring.
Genes can be either dominant or recessive. Recessive genes need two copies (one from each parent) in order to show. If there is a copy of each gene, the rat is called "heterozygous" for the trait; this means it carries the gene and can have offspring with that gene, but just looking at the rat you won't know what it is.
genetics
Ears - Regular top ears are dominant; dumbo ears are recessive. Dumbo ears are set low on the skull and stick out to the side; top ears are set higher on the skull and stick upright.
The symbol is "d":
DD = Regular
Dd = regular
dd = dumbo
Fur - Regular smooth fur is recessive; rex fur is dominant. Rex fur is curly, and can lead to balding patches as the rat ages.
Two rex genes make a double rex (which is mostly hairless, with a bit of fur on the nose and rump).
The symbol is "Re":
ReRe = double rex
Rere = rex
rere = smooth fur
Color - "black-based" (solid) colors are recessive; agouti-based colors are dominant. Black-based colors are solid. Agouti colors have bands of color on each hair, giving them a ticked appearance.
You can see some rat colors (along with eye colors) here.
The symbol is "a":
AA = Agouti
Aa = Agouti
aa = black
Markings - Two recessive genes make a solid-colored rat; two dominant makes a "Berkshire" type (solid color with white paws and belly); one of each accounts for all of the hooded, capped, and varigated-type colors.
You can see some of the available rat markings here.
The symbol is "H":
HH = Berkshire
Hh = Hooded
hh = self
Pink-Eye Dilute - A recessive "masking" gene that covers up any other colors or markings. Two of these recessive genes creates a pink-eye white rat (albino), while only one copy makes a siamese or himilayan-type rat.
These rats can have black eyes or red eyes, but red are much more common.
Here's some Burmese examples and a few other colors of Siamese
The symbol is "P"
PP = regular coloration
Pp = Himilayan/siamese/burmese
pp = albino
High-White Markings - A dominant gene that causes white markings such as blazes or other irregular white patches on the face or body. These white markings are linked to certain organ systems as well. This gene is homozygous lethal, meaning that two copies of it will cause the rat to die as a baby from organ failure.
Here's an explanation of megacolon and some high-white pictures.
The symbol is "W":
WW = Lethal
Ww = blaze/high white markings
ww = no blazes/high white markings
Putting It All Together
So, for example, a standard black-hooded rat's genotype would be:
DD rere aa Hh PP ww
A berkshire agouti with dumbo ears would be:
dd rere AA HH PP ww
The symbol is "d":
DD = Regular
Dd = regular
dd = dumbo
Fur - Regular smooth fur is recessive; rex fur is dominant. Rex fur is curly, and can lead to balding patches as the rat ages.
Two rex genes make a double rex (which is mostly hairless, with a bit of fur on the nose and rump).
The symbol is "Re":
ReRe = double rex
Rere = rex
rere = smooth fur
Color - "black-based" (solid) colors are recessive; agouti-based colors are dominant. Black-based colors are solid. Agouti colors have bands of color on each hair, giving them a ticked appearance.
You can see some rat colors (along with eye colors) here.
The symbol is "a":
AA = Agouti
Aa = Agouti
aa = black
Markings - Two recessive genes make a solid-colored rat; two dominant makes a "Berkshire" type (solid color with white paws and belly); one of each accounts for all of the hooded, capped, and varigated-type colors.
You can see some of the available rat markings here.
The symbol is "H":
HH = Berkshire
Hh = Hooded
hh = self
Pink-Eye Dilute - A recessive "masking" gene that covers up any other colors or markings. Two of these recessive genes creates a pink-eye white rat (albino), while only one copy makes a siamese or himilayan-type rat.
These rats can have black eyes or red eyes, but red are much more common.
Here's some Burmese examples and a few other colors of Siamese
The symbol is "P"
PP = regular coloration
Pp = Himilayan/siamese/burmese
pp = albino
High-White Markings - A dominant gene that causes white markings such as blazes or other irregular white patches on the face or body. These white markings are linked to certain organ systems as well. This gene is homozygous lethal, meaning that two copies of it will cause the rat to die as a baby from organ failure.
Here's an explanation of megacolon and some high-white pictures.
The symbol is "W":
WW = Lethal
Ww = blaze/high white markings
ww = no blazes/high white markings
Putting It All Together
So, for example, a standard black-hooded rat's genotype would be:
DD rere aa Hh PP ww
A berkshire agouti with dumbo ears would be:
dd rere AA HH PP ww
