Coat Color Genetics Primer, aka "What color will the puppies be?"
This came up in another thread but I thought I'd give this its own topic. Here is, hopefully, a much easier to understand guide and "cheat sheet" for figuring out color possibilities in a litter of Japanese Akitas.
Solution: 100% non-white × 50% red = 50% red
Example: Given two dogs that meet the criteria of (c) and (e), what are the odds of having a red puppy?
Solution: 50% non-white × 0% red = 0% red
Example: Given two dogs that meet the criteria of (b) (f) and (j), what are the odds of having a normal coat brindle male puppy?
Solution: 75% non-white × 75% brindle × 75% normal coat × 50% male = ~21% normal coat brindle male.
Example: Given two dogs that meet the criteria of (b) and (g), what are all the possible colors and probabilities for the litter?
Solution:
- 25% white
- 75% non-white × 50% red = 37.5% red
- 75% non-white × 50% brindle = 37.5% brindle
Example: Can two red dogs have white or brindle puppies?
Solution: If the parents meet the criteria for (b) there may be white puppies (25% chance). However, the dogs fit (h) by definition so brindle is not possible.
Before you begin you must know the genetype of the dogs in question. This is the dog's genetic makeup, not its outward appearance.Example: Given two dogs that meet the criteria of (a) and (g), what are the odds of having a red puppy?
There are a few circumstances when you can determine coat color genes just by looking at the dog or its pedigree:
a) If the dog is white its alleles at the E Locus are e/e
b) If the dog is red or has two red parents its alleles at the K Locus are ky/ky
c) If the dog is red or brindle but has a white parent its alleles at the E Locus are E/e
d) If the dog is brindle but has a red parent its alleles at the K Locus are kbr/ky
To know any more about the dogs' genotypes you must do genetic testing. You can order the E Locus and K Locus tests from VetGen:
-- http://vetgen.com/ordertests.aspx?id=Akita
The S Locus test is also available if you wish to determine if your dogs carry the long coat gene.
Genotype Phenotype Notes
E/E kbr/kbr brindleⁿᵇ Cannot have red or white puppies
E/E kbr/ky brindleⁿᵇʳ Cannot have white puppies
E/E ky/ky redⁿʳ Cannot have white puppies
E/e kbr/kbr brindleⁿʷᵇ Cannot have red puppies
E/e kbr/ky brindleⁿʷᵇʳ
E/e ky/ky redⁿʷʳ
e/e kbr/kbr whiteʷᵇ Cannot have red puppies
e/e kbr/ky whiteʷᵇʳ
e/e ky/ky whiteʷʳ
ⁿ Carries non-white. None-white is dominant and only one parent needs to carry it.
ʷ Carries white. White is recessive and both parents must carry it.
ᵇ Carries brindle. Brindle is dominant and only one parent needs to carry it.
ʳ Carries red. Red is recessive and both parents must carry it.
»»» IMPORTANT «««
»»» If a dog is white it will mask the non-white (red or brindle) color. «««
»»» A dog is genetically red or brindle even if its not visible! «««
1.) Find the probability that a puppy will be white or non-white:
(a) If either parent does not carry white 0% of the puppies will be white, 100% non-white.
(b) If both parents are non-white carrying white odds are 25% white, 75% non-white.
(c) If one parent is white and the other non-white carrying white odds are 50% white, 50% non-white.
(d) If both parents are white 100% of the puppies will be white, 0% non-white.
2.) Find the probability that a puppy will be red or brindle:
(e) If either parent does not carry red 0% of the puppies will be red, 100% brindle.
(f) If both parents are brindle carrying red 25% of the puppies will be red, 75% brindle.
(g) If one parent is red and the other brindle carrying red 50% of the puppies will be red, 50% brindle.
(h) If both parents are red 100% of the puppies will be red, 0% brindle.
3.) Optionally, find the probability that a puppy will have long coat or normal coat:
(i) If either parent does not carry long coat 0% of the puppies will be long coat, 100% normal coat.
(j) If both parents are normal coat carrying long coat 25% of the puppies will be long coat, 75% normal coat.
(k) If one parent is long coat and the other normal coat carrying long coat 50% of the puppies will be long coat, 50% normal coat. »»» NOT RECOMMENDED «««
(l) If both parents are long coat 100% of the puppies will be long coat, 0% normal coat. »»» NOT RECOMMENDED «««
4.) Optionally, find the probability that a puppy will be male or female:
-- Odds are 50% of the puppies will be male, 50% female.
5.) Multiply all of the values together to get the probability of a specific combination occuring.
Solution: 100% non-white × 50% red = 50% red
Example: Given two dogs that meet the criteria of (c) and (e), what are the odds of having a red puppy?
Solution: 50% non-white × 0% red = 0% red
Example: Given two dogs that meet the criteria of (b) (f) and (j), what are the odds of having a normal coat brindle male puppy?
Solution: 75% non-white × 75% brindle × 75% normal coat × 50% male = ~21% normal coat brindle male.
Example: Given two dogs that meet the criteria of (b) and (g), what are all the possible colors and probabilities for the litter?
Solution:
- 25% white
- 75% non-white × 50% red = 37.5% red
- 75% non-white × 50% brindle = 37.5% brindle
Example: Can two red dogs have white or brindle puppies?
Solution: If the parents meet the criteria for (b) there may be white puppies (25% chance). However, the dogs fit (h) by definition so brindle is not possible.
Comments
It seems like white in Akita (and even as seen in Kai) may be inherited in a slightly different way than I was taught, as I believe C/I was co-dominant (white to red, for instance, would produce a lighter red/gold), or maybe I was taught a flawed system. I always like learning more, so seeing all the probability written out is really awesome! Thank you so much!
The C Locus in theory accounts for the wide range of shades seen in a red Japanese Akita including cream, apricot, gold, orange, and brown/burnt orange. It is possible but unlikely for a "white" Japanese Akita to be an extremely dilute sable dog caused by the chinchilla genes. Such a dog might be distinguished by black whiskers or a few ticked hairs in the fur; dogs that are white due the alleles at the E Locus cannot produce black pigment in hair follicles.
The C Locus is probably also responsible for causing silver brindles, since it dilutes only the red hairs. Thus, silver brindles may produce poorly pigmented red puppies if bred to a red dog.
Recently there has been talk about a pheomelanin intensity gene at another locus called the I Locus. This gene may determine the strength of the pigment in a recessive yellow dog. Many breeds carry recessive yellow, but it is expressed in a wide range of shades including white (Japanese Akitas, Samoyeds), gold (Golden Retrievers, Yellow Labradors), and chestnut (Irish Setters). Some breeds show a great deal of variation, such as Golden Retrievers which can range from a pale cream to a deep amber. Others show very little variation like Samoyeds.
It may be worth noting that at the middle of the last century there was a "yellow" color allowed for Japanese Akitas. These may have been recessive yellow dogs like today's whites, but with more intensity at the I Locus.