Black Genetics
In a Silver Fox, Black is the dominant color. It only takes one dominant "B" (Black) and one dominant "D" (dense) for a rabbit to be a phenotype Black—phenotype is the obvious genetics from the color seen as in B_D_ —however, because of the hidden genetics there are four genotypes that show Black:
In a Silver Fox, Black is the dominant color. It only takes one dominant "B" (Black) and one dominant "D" (dense) for a rabbit to be a phenotype Black—phenotype is the obvious genetics from the color seen as in B_D_ —however, because of the hidden genetics there are four genotypes that show Black:
- BBDD - Black with all dominant genes or a Double Homozygous Black that will always throw only Blacks, because the offspring must have a dominant "B" and a dominant "D".
- BBDd - Black carrying Dilute. This rabbit will throw Blacks and may throw Blues if bred with another rabbit with "d."
- BbDD - Black carrying Chocolate. This rabbit will throw Blacks and may throw Chocolates if bred with another rabbit with "b."
- BbDb - Black carrying Dilute and Chocolate, or Black Double Heterozygote. It also may be called Heterozygous Black or Black Heterozygote. This rabbit may throw any of the four colors depending on the genotype of the other rabbit.
Homozygous means the same alleles on the genotype, whether dominant or recessive as in "BB" or "bb." In the case of the Black Silver Fox only the BBDD genotype is a Double Homozygote with the least diversity. On the opposite side, the greatest genetic diversity of the "B" and "D" loci is hidden in the Black of a Double Heterozygote. While appearing Black, this genotype also carries "b" Chocolate and "d" Dilute.
BbDd-Double Heterozygous Black x BbDd-Double Heterozygous Black
Breeding two Black Heterozygotes together can produce four colors but also all nine genotypes possible in the "B" and "D" loci, including Lilac! This is the only combination of Blacks that can produce a Lilac, because both parents have to have the recessive "b" and "d" genes to produce the bbdd-Lilac (which also is a Double Heterozygote, but for the recessive genes).
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
If two Blacks, with unknown hidden genes as with B_D_, have both Chocolate and Blue offspring, then both parents must be Black Heterozygotes even if there were no Lilacs produced.
BbDd-Double Heterozygous Black x bbdd-Lilac
A Heterozygous Black bred with a Lilac also can produce any of the four colors, but not every genotype. This combination cannot produce any Dominant Double Homozygotes, so when breeding BbDd-Black Heterozgote with a bbdd-Lilac only four genotypes can be produced:
- Any Black offspring must be a BbDd-Black Heterozygote.
- Any Blue offspring must be Bbdd-Blue carrying Chocolate.
- Any Chocolate offspring must be bbDd-Chocolate carrying Dilute.
- Lilac will be bbdd-Lilac because there is only one genotype for it.
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
Genetics of Black Offspring from BbDd-Double Heterozygous Black x B_D_-Black
However, when a Heterozygous Black is bred to any Black including another Heterozygote Black, the hidden genes add more mystery to the genotype, and the Black kits could be any of the four genotypes for Black, so it would need to be written as B_D_. With test breeding those unknowns may be revealed, especially with a Lilac.
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
There would be an unknown allele in the Blue-B_dd and Chocolate-bbD_ offspring of a Heterozygous Black as well, which could only be determined by test breeding. However, any phenotype Blue or Chocolate could have these same unknowns, and breeding them with a Heterozygous Black may help determine if either carries recessive alleles.
BbDd-Double Heterozygous Black x B_dd-Blue
A Heterozygous Black bred with a Blue can produce Blacks:
- BBDd-Black carrying Dilute
- BdDd-Black Heterozygote carrying both Dilute and Chocolate
And Blues:
- BBdd-Blue
- Bbdd-Blue carrying Chocolate
In addition, if the Blue is carrying Chocolate, they can also produce:
- bbDd-Chocolate carrying Dilute
- bbdd-Lilac
If any offspring are Chocolate or Lilac, then the Blue must be carrying Chocolate "Bb dd."
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
BbDd-Double Heterozygous Black x bbD_-Chocolate
A Heterozygous Black bred with a Chocolate can produce Blacks:
- BdDD-Black carrying Chocolate
- BdDd-Black Heterozygote carrying both Blue and Chocolate
And Chocolates:
- bbDD-Chocolate
- bbDd-Chocolate carrying Dilute
In addition, if the Chocolate is carrying Dilute, they can also produce:
- Bbdd-Blue carrying Chocolate
- bbdd-Lilac
If any offspring are Blue or Lilac, then the Chocolate must be carrying Dilute "bb Dd."
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
Conclusion
The Black Double Heterozygote adds a great amount of diversity and unknowns in the offsprings' genotypes, which may or may not be desired depending on breeding goals.