Dominant and Recessive Alleles
At this time, ARBA shows only allow Black Silver Foxes to compete, however Silver Foxes can come in four main colors: Black, Chocolate, Blue, Lilac (as well as two usually unwanted colors White and Tort). Double Homozygous Black has all the dominant genetics and on the opposite side, Lilacs have all the recessive genetics. There are four genotypes that will present as Black, two as Chocolate, two as Blue, and only one possibility will present as Lilac.
At this time, ARBA shows only allow Black Silver Foxes to compete, however Silver Foxes can come in four main colors: Black, Chocolate, Blue, Lilac (as well as two usually unwanted colors White and Tort). Double Homozygous Black has all the dominant genetics and on the opposite side, Lilacs have all the recessive genetics. There are four genotypes that will present as Black, two as Chocolate, two as Blue, and only one possibility will present as Lilac.
For the purpose of this article, the focus with be on only two loci of the genotype, "B" and "D". The upper case letters are the dominant alleles and are always written first, if there is a dominant gene. The lower case letters are the recessive gene and always written after the dominant gene, if there is a dominant gene. To understand the value of a Lilac, it is necessary to understand hidden dominant and recessive alleles in which there are four combinations in the genotype of a rabbit showing Black.
The B-locus has two possible alleles. The dominant "B" standing for "Black" and the recessive "b" standing for "Chocolate."
The D-locus stands for density or dilution of the base color. It also has two possible alleles. The dominant "D" standing for dense and the recessive "d" standing for dilute. Blue is a diluted Black and Lilac is a diluted Chocolate.
The B-locus has two possible alleles. The dominant "B" standing for "Black" and the recessive "b" standing for "Chocolate."
The D-locus stands for density or dilution of the base color. It also has two possible alleles. The dominant "D" standing for dense and the recessive "d" standing for dilute. Blue is a diluted Black and Lilac is a diluted Chocolate.
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
|
||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
There must only be one "B" and one "D" gene to show Black with no dilution. Since both letters are dominant, the second alleles may not be known so it might be written with a question mark, an underscore, or a dash after the letters. I prefer underscores: B_ D_.
The Four Genotypes of Black
As the chart below shows, there are four genotypes that will show Black and it must be remembered that when breeding two rabbits, the offspring receives one allele for each locus from the father and the likewise from the mother:
bbdd-Lilac x B_D_-Black
There are combinations of breedings that will eventually determine the hidden alleles, but those hidden alleles can be exposed in as little as one breeding with a Lilac, greatly simplifying the process. This is because a Lilac, bbdd, has only recessive alleles on the "B" and "D" loci.
In other words, if a bbdd-Lilac is bred to a B_D_-Black producing:
bbdd-Lilac x B_dd-Blue
Breeding a Lilac with B_dd-Blues and bbD_-Chocolates can also reveal the remaining hidden gene on each and it is far more limited in what colors are possible because there is only one locus in question.
In Blues, the "D" locus must be "dd" and there must be a dominant "B" in the B-locus so the remaining question whether the unknown gene on the B-locus is dominant or recessive. The chart below shows the only two possible genotypes of crossing a Lilac with a Blue.
A Lilac bred with a Blue will reveal if the Blue is carrying Chocolate:
A Lilac bred with a Chocolate will reveal if the Blue is carrying Chocolate:
bbdd-Lilac x bbdd-Lilac
If a Lilac is bred with another Lilac, the only possibility is bbdd-Lilac offspring since neither parent would have any dominant "B" or "D" alleles to contribute.
All Lilac Offspring are Both Chocolate and Dilute Carriers
As seen in the chart below, it should be noted that all Lilac offspring are always both Chocolate and Dilute carriers, regardless of their presented color. This diversity may or may not be a desired trait in the breeding program. However, as previously discussed, breedings with a Lilac may be the best way to identify a BBDD-Black that not only has a showable color but would only produce showable colored Blacks. The BBDD-Black Silver Fox rabbit could be more valuable especially as a breeder for a Black-only line of show quality rabbits.
The chart below shows that each of the four colors in the offspring of a Lilac will only have one possible genotype regardless of the genotype of the other parent. In other words, all the Black offspring from a Lilac parent will be BbDd; all Blues, Bbdd; and all Chocolates, bbDd. Lilac always has only one possibility, bbdd.
The Four Genotypes of Black
As the chart below shows, there are four genotypes that will show Black and it must be remembered that when breeding two rabbits, the offspring receives one allele for each locus from the father and the likewise from the mother:
- BBDD - Black with all dominant alleles 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".
- BbDd - 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.
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
bbdd-Lilac x B_D_-Black
There are combinations of breedings that will eventually determine the hidden alleles, but those hidden alleles can be exposed in as little as one breeding with a Lilac, greatly simplifying the process. This is because a Lilac, bbdd, has only recessive alleles on the "B" and "D" loci.
- bbdd-Lilac x BBDD-Black = all Blacks. Genetically, all the offspring will be BbDd-Heterozygous Blacks, carrying both chocolate and blue.
- bbdd-Lilac x BBDd-Black carrying Dilute = Blacks and Blues. Genetically, the offspring will be either BbDd-Heterozygous Blacks or Bbdd-Blues carrying Chocolate.
- bbdd-Lilac x BbDD-Black carrying Chocolate = Blacks and Chocolates. Genetically, the offspring will be either BbDd-Heterozygous Blacks or bbDd-Chocolates carrying Dilute.
- bbdd-Lilac x BbDd-Heterozygous Black = all color combinations, including Lilac. Genetically, the offspring will be all the combinations listed above plus bbdd-Lilac.
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
In other words, if a bbdd-Lilac is bred to a B_D_-Black producing:
- only Black, then the B_D_ Black parent would probably be BBDD-Black, although future breedings would confirm that better.
- any Blue, then the B_D_ Black parent is carrying Dilute as B_Dd .
- any Chocolate, then the B_D_ Black parent is carrying Chocolate as BbD_ .
- any Lilac, then the B_D_ Black parent must be a BbDd-Heterozygous Black.
- Chocolate and Blue, then the B_D_ Black parent must be BbDd-Heterozygous Black, even if there are no Lilacs.
bbdd-Lilac x B_dd-Blue
Breeding a Lilac with B_dd-Blues and bbD_-Chocolates can also reveal the remaining hidden gene on each and it is far more limited in what colors are possible because there is only one locus in question.
In Blues, the "D" locus must be "dd" and there must be a dominant "B" in the B-locus so the remaining question whether the unknown gene on the B-locus is dominant or recessive. The chart below shows the only two possible genotypes of crossing a Lilac with a Blue.
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
| ||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
A Lilac bred with a Blue will reveal if the Blue is carrying Chocolate:
- bbdd-Lilac x BBdd-Blue = all Blues. Genetically, all the offspring will be Bbdd-Blue carrying Chocolate.
- bbdd-Lilac x Bbdd-Blue carrying Chocolate = Blues and Lilacs are possible. Genetically, all the offspring will be Bbdd-Blue carrying Chocolate or bbdd-Lilac.
Therefore if any of the offspring are Lilac, then the Blue is a Chocolate carrier, but if all the offspring are Blue, it is likely the Blue that was bred is BBdd and does not carry Chocolate.
bbdd-Lilac x bbD_-Chocolate
In Chocolates, the "B" locus must be "bb" and there must be a dominant "D" in the D-locus so the remaining question whether the unknown gene on the D-locus is dominant or recessive. The chart below shows the only two possible genotypes of crossing a Lilac with a Chocolate.bbdd-Lilac x bbD_-Chocolate
Black
|
BB DD
|
BB Dd
|
BB dd
|
Blue
|
Bb DD
|
Bb Dd
|
Bb dd
|
||
Chocolate
|
bb DD
|
bb Dd
|
bb dd
|
Lilac
|
A Lilac bred with a Chocolate will reveal if the Blue is carrying Chocolate:
- bbdd-Lilac x bbDD-Chocolate = all Chocolates. Genetically, all the offspring will be bbDd-Chocolate carrying Dilute.
- bbdd-Lilac x bbDd-Chocolate carrying Dilute= Chocolates and Lilacs are possible. Genetically, all the offspring will be bbDd-Chocolate carrying Dilute or bbdd-Lilac.
bbdd-Lilac x bbdd-Lilac
If a Lilac is bred with another Lilac, the only possibility is bbdd-Lilac offspring since neither parent would have any dominant "B" or "D" alleles to contribute.
All Lilac Offspring are Both Chocolate and Dilute Carriers
As seen in the chart below, it should be noted that all Lilac offspring are always both Chocolate and Dilute carriers, regardless of their presented color. This diversity may or may not be a desired trait in the breeding program. However, as previously discussed, breedings with a Lilac may be the best way to identify a BBDD-Black that not only has a showable color but would only produce showable colored Blacks. The BBDD-Black Silver Fox rabbit could be more valuable especially as a breeder for a Black-only line of show quality rabbits.
The chart below shows that each of the four colors in the offspring of a Lilac will only have one possible genotype regardless of the genotype of the other parent. In other words, all the Black offspring from a Lilac parent will be BbDd; all Blues, Bbdd; and all Chocolates, bbDd. Lilac always has only one possibility, bbdd.
| Color of Offspring | Parents Lilac x (Genotype) |
Genotypes of Offspring |
| Black | BB DD | Bb Dd |
| Bb DD | Bb Dd | |
| BB Dd | Bb Dd | |
| Bb Dd | Bb Dd | |
| Blue | BB dd | Bb dd |
| Bb dd | Bb dd | |
| Chocolate | bb DD | bb Dd |
| bb Dd | bb Dd | |
| Lilac | bb dd | bb dd |