Monday, October 16, 2006
The May, Must, and Cannot of Color Genes
You may wish to pull up or print out the chart of 144 rabbit coat colors and their genotypes before reading this BLOG post. It will make much more sense if you are aware of the genotypes of some of the more common Holland lop colors.
From time to time, folks write me about their color gene mysteries. Most of the time, it's really no mystery. Once a few basic concepts are understood, the inquirer "sees" what's going on. Occasionally, we find an error in a pedigree. Perhaps kits were fostered and not tracked appropriately. Sometimes people change colors when they copy pedigree information.
This weekend, I saw a pedigree for one of the rabbits I pedigreed - on different paper, from a different computer program, and with a different color listed - totally inaccurate. Those types of things shouldn't happen, but they do.
But let's say that the information you have is accurate. What does it tell us about the kits we might produce?
Two Recessive Genes
"Musts" and "Cannots" come in when both parents carry two recessive genes in the same location. If you have two self rabbits (aa), for example, they must produce selfs and cannot produce agoutis or martens or tans or otters. You can eliminate 2/3 of all possible colors if you know that both parents are "aa."
Likewise, if both parents are "ee," such as with tort, blue tort, sable point, blue point, orange, fawn, ermine, blue ermine and the like, then the offspring must be also an "ee" color and cannot be an "E" color.
One of the biggest applications of this concept comes when you have a rabbit that you think might be a smoke pearl (blue sable). If neither parent has the E gene, such as found in black, blue, Siamese sable, chestnut, opal, chinchilla, and squirrel, then you cannot have a smoke pearl. You probably have a blue point.
Other Cannots
Certain genes are dominant and recessive, being in the middle of a dominant-recessive sandwich. The a-series has three genes, the c-series has five genes, and the e-series has four genes. In those cases, you cannot produce rabbits with a more dominant gene than the most dominant one possessed by a parent.
That sounds more confusing than it is. If you breed an otter and a self rabbit, you cannot produce an agouti color. If you've got a puzzler, don't even list an agouti color among the possibilities.
Likewise, if you breed a rew to a chinchilla, there's no need to consider any full colors (C-gene).
Dominant Genes
When even one parent has a dominant gene, things can become more interesting. You do not usually know what the other gene hides, unless the parents of that rabbit have given you a clue. Or perhaps previous offspring have given you the information you need.
Suppose you have a black rabbit. You know that it is aa B- C- D- E. But what are those recessive genes? Could this rabbit produce a blue? a tort?
First, look at its parents. If one of them is a tort, which frequently happens, you know that that parent only had a recessive "e" gene to donate. So you can update the genes thus: aa B- C- D- Ee. Now you can see that this rabbit can easily produce a tort.
Perhaps the other parent was blue. Therefore, that parent would only have had a recessive "d" to donate. Now we can update the genotype again: aa B- C- Dd Ee.
But maybe one parent was a sable point instead. Then we can say that the second c-series gene is either a sable gene, himi gene, or rew gene (the sable gene plus the rew or himi gene makes for a properly-gened sable point - we wouldn't know which of these was inherited).
Ferreting It Out
I have a doe that produced a REW in one litter. She's a tort, so I can update her genotype to Cc. In another litter, she produced a sable point. I can update the sire's genotype to Ccchl (full color plus the sable gene).
That's one example of combining information from different litters to determine what those recessive genes can be.
When you have puzzlers, first list the genotype for the rabbit. Fill in as much as you can from the parents. Next, go to the chart of 144 rabbit coat colors. Eliminate all of the "cannots" based on the genotype that you know. Then, eliminate the "cannots" based on your visual information. If it is a light-colored rabbit, you can strike black and Siamese sable, for example.
By this time, you will have a very small pool of colors to work with, I'm guessing. It's time to whittle away a bit more.
If you are not specifically working with chocolates in your barn or in the lines you work with, you can assume that the rabbit is BB. Even though it is theoretically possible that chocolate hid for generations, it's pretty rare unless you specifically go after it.
White or light bellies versus colored bellies will give you a clue about the a-series gene. So will eye circles, nose markings, ear lacing, and triangles behind the head. Eye color will clue you in to the rew or himi gene. A ruby glow to the eye might give you a hint about recessive c-series genes (usually REW).
If the color is different at the extremities, look at the c-series and e-series for answers there. Both the sable gene and "e" gene have that effect.
Deciding The Color
Usually, you can limit the choices based on your genetic information. Then the visual inspection of the rabbit confirms the color for you. But what if you narrow it down genetically to a blue point, blue, and smoke pearl, for example? Perhaps your visual inspection doesn't convince you of one over the other. Maybe the rabbit is molty, so it doesn't appear to be one solid color, but it could be. What next?
The proof is in the pudding, or, in our case, in the kits. Breeding that rabbit to a REW will test out the c-series genes. Breeding to an "ee" rabbit should let you know about the presence of the E in the tested rabbit. Let's say you breed this bluish rabbit with a rew and get a sable point and a REW. Then you'd know that the tested rabbit is either a smoke pearl or a blue point. You could eliminate the blue, which needs a full color gene.
Next, you breed the rabbit to several torts. Let's say there are ten kits in all and none of them are black or blue. They are all sable points or torts. Then we can pretty safely assume (due to the number of kits), that the rabbit in question in an "ee" rabbit, and therefore a blue point, since smoke pearl would require the "E" gene.
Summary
If this BLOG boggled your mind, don't worry. Until you learn some of the more common genotypes, it can really be difficult to grasp. I suggest that you learn tort: aa B- C- D- ee, sable point: aa B- cchl- D- ee, black: aa B- C- D- E, blue: aa B- C- dd E-, blue point: aa B- C- dd ee, and and blue tort: aa B- C- dd ee. Even more important is to learn the relationship between the colors:
From time to time, folks write me about their color gene mysteries. Most of the time, it's really no mystery. Once a few basic concepts are understood, the inquirer "sees" what's going on. Occasionally, we find an error in a pedigree. Perhaps kits were fostered and not tracked appropriately. Sometimes people change colors when they copy pedigree information.
This weekend, I saw a pedigree for one of the rabbits I pedigreed - on different paper, from a different computer program, and with a different color listed - totally inaccurate. Those types of things shouldn't happen, but they do.
But let's say that the information you have is accurate. What does it tell us about the kits we might produce?
Two Recessive Genes
"Musts" and "Cannots" come in when both parents carry two recessive genes in the same location. If you have two self rabbits (aa), for example, they must produce selfs and cannot produce agoutis or martens or tans or otters. You can eliminate 2/3 of all possible colors if you know that both parents are "aa."
Likewise, if both parents are "ee," such as with tort, blue tort, sable point, blue point, orange, fawn, ermine, blue ermine and the like, then the offspring must be also an "ee" color and cannot be an "E" color.
One of the biggest applications of this concept comes when you have a rabbit that you think might be a smoke pearl (blue sable). If neither parent has the E gene, such as found in black, blue, Siamese sable, chestnut, opal, chinchilla, and squirrel, then you cannot have a smoke pearl. You probably have a blue point.
Other Cannots
Certain genes are dominant and recessive, being in the middle of a dominant-recessive sandwich. The a-series has three genes, the c-series has five genes, and the e-series has four genes. In those cases, you cannot produce rabbits with a more dominant gene than the most dominant one possessed by a parent.
That sounds more confusing than it is. If you breed an otter and a self rabbit, you cannot produce an agouti color. If you've got a puzzler, don't even list an agouti color among the possibilities.
Likewise, if you breed a rew to a chinchilla, there's no need to consider any full colors (C-gene).
Dominant Genes
When even one parent has a dominant gene, things can become more interesting. You do not usually know what the other gene hides, unless the parents of that rabbit have given you a clue. Or perhaps previous offspring have given you the information you need.
Suppose you have a black rabbit. You know that it is aa B- C- D- E. But what are those recessive genes? Could this rabbit produce a blue? a tort?
First, look at its parents. If one of them is a tort, which frequently happens, you know that that parent only had a recessive "e" gene to donate. So you can update the genes thus: aa B- C- D- Ee. Now you can see that this rabbit can easily produce a tort.
Perhaps the other parent was blue. Therefore, that parent would only have had a recessive "d" to donate. Now we can update the genotype again: aa B- C- Dd Ee.
But maybe one parent was a sable point instead. Then we can say that the second c-series gene is either a sable gene, himi gene, or rew gene (the sable gene plus the rew or himi gene makes for a properly-gened sable point - we wouldn't know which of these was inherited).
Ferreting It Out
I have a doe that produced a REW in one litter. She's a tort, so I can update her genotype to Cc. In another litter, she produced a sable point. I can update the sire's genotype to Ccchl (full color plus the sable gene).
That's one example of combining information from different litters to determine what those recessive genes can be.
When you have puzzlers, first list the genotype for the rabbit. Fill in as much as you can from the parents. Next, go to the chart of 144 rabbit coat colors. Eliminate all of the "cannots" based on the genotype that you know. Then, eliminate the "cannots" based on your visual information. If it is a light-colored rabbit, you can strike black and Siamese sable, for example.
By this time, you will have a very small pool of colors to work with, I'm guessing. It's time to whittle away a bit more.
If you are not specifically working with chocolates in your barn or in the lines you work with, you can assume that the rabbit is BB. Even though it is theoretically possible that chocolate hid for generations, it's pretty rare unless you specifically go after it.
White or light bellies versus colored bellies will give you a clue about the a-series gene. So will eye circles, nose markings, ear lacing, and triangles behind the head. Eye color will clue you in to the rew or himi gene. A ruby glow to the eye might give you a hint about recessive c-series genes (usually REW).
If the color is different at the extremities, look at the c-series and e-series for answers there. Both the sable gene and "e" gene have that effect.
Deciding The Color
Usually, you can limit the choices based on your genetic information. Then the visual inspection of the rabbit confirms the color for you. But what if you narrow it down genetically to a blue point, blue, and smoke pearl, for example? Perhaps your visual inspection doesn't convince you of one over the other. Maybe the rabbit is molty, so it doesn't appear to be one solid color, but it could be. What next?
The proof is in the pudding, or, in our case, in the kits. Breeding that rabbit to a REW will test out the c-series genes. Breeding to an "ee" rabbit should let you know about the presence of the E in the tested rabbit. Let's say you breed this bluish rabbit with a rew and get a sable point and a REW. Then you'd know that the tested rabbit is either a smoke pearl or a blue point. You could eliminate the blue, which needs a full color gene.
Next, you breed the rabbit to several torts. Let's say there are ten kits in all and none of them are black or blue. They are all sable points or torts. Then we can pretty safely assume (due to the number of kits), that the rabbit in question in an "ee" rabbit, and therefore a blue point, since smoke pearl would require the "E" gene.
Summary
If this BLOG boggled your mind, don't worry. Until you learn some of the more common genotypes, it can really be difficult to grasp. I suggest that you learn tort: aa B- C- D- ee, sable point: aa B- cchl- D- ee, black: aa B- C- D- E, blue: aa B- C- dd E-, blue point: aa B- C- dd ee, and and blue tort: aa B- C- dd ee. Even more important is to learn the relationship between the colors:
- blue tort is the dilute of tort,
- blue is the dilute of black,
- blue point is the dilute of sable point,
- tort and black are just alike except that black is full extension and tort is non-extension
- blue tort and blue are just alike except that blue is full extension and tort is non-extension
- sable point and Siamese sable are just alike except that Siamese sable is full extension and sable point is non-extension
- tort and sable point only differ in the c-series gene
- blue tort and blue point only differ in the c-series gene
- black and Siamese sable and seal only differ in the c-series gene
- blue and smoke pearl only differ in the c-series gene
- black and chestnut agouti only differ in the a-series gene
So when you have a puzzler, write down what you know must be there, eliminate the colors that cannot occur, and make a close visual inspection to determine the color.
Laurie Stroupe
The Nature Trail Rabbitry “Home Of Grand Champions”
Precious Pet Rabbits
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