I bred a broken chocolate to a blue and got a litter of 7 kits. Four solid black and 3 broken black.
Aren't things like this fascinating, on the surface, it seems highly unlikely that you could cross a blue and a chocolate and get all black kits (some broken and some solid).? But, once you understand the underlying principles, it suddenly makes sense. Every rabbit has two copies of each gene, one donated by each parent. Each gene has two or more options to choose from. The 'boss', or
dominant option, only needs one copy to strut its stuff and be seen. The more shy
recessive option will require both copies to be the same recessive choice in order to have enough strength to be seen.
One of the rabbit color genes is coded 'B' for black. There are only two options on that gene--the 'boss', or dominant choice is black (which includes any of the black-based colors like blue, opal, or blue tort). The recessive choice is brown (which includes all of the chocolate-based colors like self chocolate, lilac, lynx and chocolate tort.)
Another gene is coded 'D' for Dense/Dilute. The dominant option is full dense color, which means that the full amount of pigment for that color is sent to the hairshaft. The recessive is dilute, which means only part of the pigment is manufactured, and the color is more pastel. With two recessive dilute genes (coded with a lower-case 'd'), black becomes blue, chocolate fades to lilac, chestnut agouti becomes opal, chocolate agouti lightens to lynx, orange agouti becomes fawn/cream (name depends on breed).
Your crossed a blue (dominant black, recessive dilute) with a chocolate (brown is recessive to black, and dominant dense color). It appears that both rabbits had two copies the same of each gene. Sometimes, when you have a dominant gene paired with a recessive, you can only see the dominant gene, and don't know about whether it is paired with another dominant or a recessive version, since it only takes one dominant copy for it to show itself. That's how you can sometimes end up with odd colors in a litter--there were other hidden recessives that combined. In your case, each kit got one gene from each parent.
That means that the blue can only donate a dilute gene, because it has two of them (coded
dd). The chocolate can only donate a recessive brown, because it has two of them (
coded bb). The blue is black + dilute. Black is dominant, so you know it has at least one dominant black gene (coded with a capital
B to show it is dominant, recessive traits are coded with a lower case letter.) The chocolate is full dense color (not lilac), so you know it has at least one dominant dense gene (coded with a capital
D). You don't know what the dominant genes are paired with, until you have kits. In this case, the chocolate donated dominant Dense color to EVERY kit, suggesting it is
DD and has both genes with dense color. The blue donated dominant black, and EVERY kit shows it, which suggests it is
BB and has both genes with black-based color.
The fun thing is, now every single kit will be
Bb Dd, each carrying a recessive trait behind the dominant. Which means depending on how they combine, if you bred them together, you could get black, blue, chocolate or lilac kits. Broken is a separate gene, and it is dominant. Proper broken pattern requires one broken copy, and one solid recessive (two broken copies creates a 'Charlie', a mostly white rabbit with a few stray colored spots, only 10% or so color, and so not showable.) Your broken kits, since they were a cross of a dominant broken x recessive solid, will have the proper
En en genetics (the code is 'En', short for
English spotting, as in the English Spot breed.) Crossing these spotted kits to a solid will give you a 50/50 chance of more brokens.
Do remember that genetics is a game of chance. When we say you have a 50/50 chance, that's the odds over a large number of births. In reality, Lady Luck can throw whatever she wants. Your rabbits could both have hidden recessives, and it could just be that Lady Luck picked all the dominant traits this time. Which is why it is sometimes said it takes at least three litters to be reasonably sure of what the litter is telling you about the genetics of the parents. Some litters are all girls, or all boys, even though the odds are closer to 50/50. After all, people sometimes actually hit the jackpot, have a run at the gaming table winning multiple times in a row, or have persistent good or bad luck. That's part of the fun, trying to figure out the odds vs. what you really get, it's often such a surprise.
