Cheat Sheet: Understanding the D Locus (Dilution) in Self Rabbits

Although the D Locus (dilution) does affect rabbits who are Agouti or Tan/Otter, for this introduction let's stick to Self rabbits. As we know from this previous discussion of the A Locus, a Self rabbit is a solid-colored animal.

We will discuss the D Locus and how it affects Agouti and Tan rabbits in future scenarios.

The effects of the D Locus on chocolate rabbits is to lighten the color to lilac. It is exactly the same inheritance as black to blue: dilution is a simple recessive. However if you wish to add an element of complexity, you can "stack" genes; let's say you have two black rabbits. Visually, they are just black. However if both of them are heterozygous for dilution, AND both are heterozygous for the B Locus (recessive-Chocolate), you may get any of the following in a litter: black, blue, chocolate, AND lilac!

CLIFF'S NOTES FOR DILUTION ON SELF:

If you don't want to worry about Punnett squares or inheritance and just want to know what you will get through breeding, here is a basic rundown:

For this example, "Black" signifies a homozygous full-color (D/D) rabbit; "Black Carrying Blue" signifies a heterozygous for dilute (D/d) rabbit; "Blue" signifies a rabbit who is homozygous for dilution (d/d).

Black + Black = 100% Black. NO EXCEPTIONS.

Black + Black Carrying Blue = 50% Black, 50% Black Carrying Blue.

Black + Blue = 100% Black Carrying Blue. NO EXCEPTIONS.

Blue + Black Carrying Blue = 50% Black Carrying Blue, 50% Blue.

Blue + Blue = 100% Blue. NO EXCEPTIONS.

Black Carrying Blue + Black Carrying Blue = 50% Black Carrying Blue, 25% Black, 25% Blue.

Now let's consider rabbits homozygous for chocolate.

For this example, "Chocolate" signifies a homozygous full-color (D/D) rabbit; "Chocolate Carrying Lilac" signifies a heterozygous for dilute (D/d) rabbit; "Lilac" signifies a rabbit who is homozygous for dilution (d/d).

Chocolate + Chocolate = 100% Chocolate. NO EXCEPTIONS.

Chocolate + Chocolate Carrying Lilac = 50% Chocolate, 50% Chocolate Carrying Lilac.

Chocolate + Lilac = 100% Chocolate Carrying Lilac. NO EXCEPTIONS.

Lilac + Chocolate Carrying Lilac = 50% Chocolate Carrying Lilac, 50% Lilac.

Lilac + Lilac = 100% Lilac. NO EXCEPTIONS.

Chocolate Carrying Lilac + Chocolate Carrying Lilac = 50% Chocolate Carrying Lilac, 25% Chocolate, 25% Lilac.

Now do recall that these two Loci, the B Locus and D Locus, can "stack." Sometimes you can get a rainbow litter from two solid black rabbits! If you do get a recessive expression on a kit, it would be a good idea to mark it on the parents' pedigrees for future reference.

For example, I bred a blue doe (d/d) to a black buck carrying dilution (D/d). I expected black and blue kits only. To my surprise, there was also a chocolate kit in the litter!!! I hadn't know that BOTH my blue doe AND my black buck carried recessive chocolate!!! Thus my doe was d/d, B/b and my buck was D/d, B/b. Because that chocolate kit's mother was blue, but the kit was chocolate instead of lilac, she was genetically D/d, b/b. I marked on the pedigrees of each parent that they are apparently heterozygous for the B Locus! None of their ancestors on their pedigrees had been either chocolate or lilac, so the genes were "hidden" for over three generations.

Now let's look at how all of those genes "stack" together. If necessary, please refresh your memory of the A Locus, and the B Locus before we begin.

The blue doe in the above example is homozygous for self and dilution, heterozygous for chocolate. Thus, genetically, she is a/a, B/b, d/d. 

The black buck is homozygous for self, and heterozygous for dilution and chocolate. Thus, genetically, he is a/a, B/b, D/d.

The chocolate kit is homozygous for self and chocolate, heterozygous for dilution so, genetically, is a/a, b/b, D/d.

Starting to make sense? I hope so! 

Lastly, something to keep in mind is that the percentages listed above are for EACH KIT, not the litter as a whole unless the result is 100% foolproof. This means that each kit in a litter of, say, blue to black carrying blue mating, has a 50% chance of being blue. As such actual litter percentages may vary!

If you have any further questions, please feel free to comment below!