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Aa genotype interactions; Sometimes genes can't hide
Topic Started: Jun 25 2015, 07:57 PM (489 Views)
wildrabbits
Hopelessly Addicted to the Fuzz
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Over the years most of my pairings have been color crosses of self to pearl or tort to chinchilla resulting in many Aa with Ee/ee as well as Ccchd gene interactions in the offspring. I have noticed that many of these interactions are indeed VERY visible with even the most dominant heterozygous colors. Here are two examples of unrelated AaEe genotypes in Adulthood

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wildrabbits
Hopelessly Addicted to the Fuzz
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Notice the identical marking in color from light to dark on the sides of the chestnut and opal males
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wildrabbits
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Now here at the opposite end of the color spectrum we have a male AAcchdcee and his daughter from a blue self female.
The daughter shown is genotype Aacchdcee. Notice how the father is almost entirely white while the daughter has a self marked face and smut yet both have the agouti ear lacing on the ear tips.

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wildrabbits
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Here is a castor rex during his youth. He is carrying tort AaEe, notice how his flank is lighter exactly where the marking on a tort would be darker.
On the second pic is a female torted fawn(Aaee) you see the same pattern with the enlightened tort markings on the flanks.
The third pic is of a male torted fawn with once again the exact same enlightened markings on flanks

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All rabbits pictured have the typical agouti ear lacing throughout life. These 3 rabbits are pictured at young age to give the understanding of how best to spot "ae" carriers from young age. The Aa_e phenotype markings/patterns consistently repeat themselves at the legs.

Smut and ticking from Aa genotypes tends to be more noticeable with cchdee.
Smut and ticking usually isn't expressed much at all until older age. Season seems to effect colors as well
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reh
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Get the Duct Tape, Stat!
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In the first two images the rabbits are obviously molting (like this one: Posted Image ), having shorter, new fur on back and longer, old one on side.

If you cross differend breeds/colors, you not only cross AE with ae, but also different selected for modifiers. f.e. good torts are selected for dark color, red rabbits are selected for as few smut as able. I dont know how its handled in countries where colors are crossbreed, but at least in germany what you show here is very normal after crossing.

Agoutis and reds f.e. have to be selected for even pheomelanin shades about the body to match the SOP, but torts dont have to. But the red intensity is NOT caused by the agouti gene. A only switches pigment production from dark eumelanin to light pheomelanin, but it doesnt influences the shade of the light pigment. So A causes all the white color in chinchilla, but it dont cause the white versus red differences in agouti. A dont causes all of the so called agouti markings. F.e. the red color of lap spots is also present on torts and the light belly, lighter eye circles and so one are only covered up by the dark pigment present in torts due to the temperature sensitivity of e and the missing A, which prevents most of its effect in Aee. In animals with a total loss of function mutation of Extension there is no difference between Aee and aaee animals.
Yes, the dark parts in torts partly match the light parts in unselected agoutis, but are they caused by A or even Aa? I think not so.

I dont know which factors may be in play with this patterning. Some candidates are skin thickness, hair thickness/deep of hairfollicles, skin temperature (for black color). There are factors regulating the areas in which different agouti signaling protein transkripts work, which may regulate other factors too, ..., ..., ...

The white with the dark nose is somewhat striking, but i have had very dark tort satinangoras as well as such looking like a himi in red. I had fairly clean reds and such who nearly look like a tort.

AAee rabbits: Posted Image Posted Image
aaee rabbits: Posted Image Posted Image Posted Image
www.rabbitcolors.info - Images and Gene Codes
www.satinangora.de
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NeuBunny
Genetics Geek!
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Interesting ... I'm not at all convinced this is just molting... I currently have a castor minirex baby (out of an opal x tort) that shows the same flank shading. Currently just 7 weeks old, so not molting but the baby coat fully in. So that would be AaEe and matching the pattern you see. I spent quite some time worrying it was a torted otter (mom is Aat) but the ring color is too pronounced for that (actually has better ring color than mom now).

On the other hand, I've had plenty of perfectly nice fawns (with no sign of such shading) that threw tort kits ... and nice agoutis that threw self. So JUST Aa isn't sufficient to explain the 'breakthrough shading'. I don't think just AaEe would be sufficient to explain it either ... though adding Ww (heterozygous wideband) or other modifiers that minimize tip color might.

Good torts and reds depend on large number of modifier genes - they are heavily selected for modifiers that remove 'smut' and alter undercolor. Although crossing colors within breeds is common and acceptable in the US (even among show breeders - 'type before color' is a mantra ... subtle shading on an agouti minirex will cost you less than 5 points on the showtable - negligible compared to any other type or coat factor), virtually every guide I've seen to raising show agoutis warns against crossing them with non-extension ... because 'the modifiers' mess up ring definition (and I did it anyway ... the tort buck is the only minirex in our barn that doesn't have weak shoulders ... and the best typed minirex we own hands down - looks to have paid off in the sister, which is a gorgeous little black otter doe). And the minirex guide to color crossing warns against mixing reds and torts 'because they have different modifiers' - crossing reds and torts makes BOTH the red and tort offspring 'smutty'.

Bottom line, I think that when you see this sort of shading the offspring are Aa (with modifiers) but Aa rabbits without the tort modifiers won't show the shading.

Point of curiosity ... if you still have any of the pictured agouti rabbits, do a quick comparison of the hairs from the back versus the hairs from the flank (I'm planning to do the same from our little one when she is a bit bigger). Is the difference in the relative band widths or in the intensity of the phaeomelanin? If the difference is in bandwidth, this is probably a modifier similar to w (acting on A and bandwidth) ... if intensity of phaeomelanin, it is more likely similar to rufus factor or other color intensity modifiers.

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NeuBunny
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On your 'whites' ... ermine are highly variable (one of the reasons they aren't accepted for show ... though I'm rooting for Czech Frosties to pass soon). I'm not sure what modifiers are involved, but at a recent exhibition show of the Czech Frosties (presumably all AAchdchdee and selected for consistency) I saw animals both lighter than your buck and darker than the daughter.
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reh
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Posted Image
www.rabbitcolors.info - Images and Gene Codes
www.satinangora.de
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wildrabbits
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The first Chestnut rabbit I have pictured came from a Thuringer male and chinchilla female so obviously has to carry AaEe to be a chestnut color coming from a tort parent. The second Opal male was bred from a pearl(3rd male I pictured) and a self blue mother. Again to be Opal color from a Pearl and a self parent it has to be AaEe. I can show pics of the parents when paired to further verify.

Molting or not AaC_Ee and AaC_ee has a very specific effect which has always produced that exact same tort pattern on the flanks during youth and ONLY the "a" gene is known for making this specific pattern. Some things can and do hide this pattern though. "bb", "dd", and fur type can all lighten the "a" tort marking as you unknowingly pointed out with some of your pics Reh. F.e. Posted Image Posted Image
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wildrabbits
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On the ermines "a" always seems to force the expression of smut and sparse dark colors. Aacchd_ee does not seem to show that indisputable tort marking pattern on the side flanks in youth as AaC_ee Posted Image or sallander does Posted Image

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wildrabbits
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It is VERY important to note that ermines in particular are suppose to show how cchd IS a codominant gene just like cchl and WILL express different coloring when paired with cchd, cchl, ch, or c. I think AAcchdceeww makes for some of the whitest pearls with BEW gene further whitening. I have never seen an atatcchdcee rabbit to compare though..

It is also important to note that opal AaC_ddEe doesn't seem to show tort marking pattern around the flanks during youth as pronounced when compared to AaC_D_Ee or AaC_ddee. Even AabbC_Ee(chocolate chestnut carrying tort displays the tort/marking pattern in a much more pronounce manner than Opal... AaEe Opal seems to naturally blend the colors together quite well on the coat with slightly lighter sides.

As far as pheomelanin goes my comments are very limited from what I currently know due to cchd interactions being so frequent in my pairings of choice.

Between the 4 opal rabbits I have they all seem to be different phenotypes directly resulting from different genotypes which has been much easier to study as they have matured.
I have not yet test bred 3 of them but would describe those genotypes as follows
1)AaCcddEe for sure from her parents(AaBbCcchdddee father with aaBbccDdEe mother)

2)AatC_ddE_(seems overall deeper/darker blue and martenized from blue otter mother, may carry cchd or c and e)

3)A_C_ddEe for sure from Aabbcchdcddee mother and AaBbCCDdEe father but also seems to be ww?. he now carries much more red overall than all other opals and seems red on inside of ears...this rabbit was VERY white instead of red during youth guessing he carries cchd and hair was pretty much white half way up hair shaft..not sure if AA or Aa on this guy! He almost looked like some sort of blue/lilac or lilac/opal mix for quite some time during his youth
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reh
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Get the Duct Tape, Stat!
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Maybe it helps if you take some good! images of the rabbits in question to see what you talk about. There are some tips in the help page of rabbitcolors for taking images. At least i cannot judge much on too dark or unsharp pics.

I am not sure if i am not able to explain what i mean or you are not able to understand it.

Please, can you use different words for different things? Tort pattern is dark whereas the pattern in agouti/red similar in location to the tort pattern is light.

I dont know which sort of pattern you mean for the Aacchd_ee not showing it, but its not supposed to show dark tort pattern for beeing A and its not able to show the light pattern either since it has no yellow to have different intensities of it for beeing cchd.

I dont doubt your agoutis beeing Aa, i doubt the pattern you watched beeing caused by Aa.

Young rabbits seem to somethimes have fewer red then older ones. F.E. i was told young red satins (german line, truebreeding color, no c-anything) are lighter as kits and darken later. This effect may be stronger in the lighter parts.

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ONLY the "a" gene is known for making this specific pattern
I dont think so, as i explained above.

Its absolutely normal for bb to "hiding" the pattern as bb only influences eumelanin and this becomes lighter and resembles more the reddish color and so blents in.
Similar for dilution which causes a clumping in pigment granules and this changed pigment distribution may lead to a similar effect by lighten up the more intense color more then the faded one.

How looks a "martenized" agouti?

How will you call the pattern in this image?
Posted Image
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Edited by reh, Jun 27 2015, 05:45 AM.
www.rabbitcolors.info - Images and Gene Codes
www.satinangora.de
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NeuBunny
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Are those straight thermal images? Cool! Really shows the temperature sensitivity which drives the shaded markings (and often the 'smut' patterns too). Reversed from normal thermal colors as the points are cool. Can I borrow this for our 4H leader?

I know ch is temperature sensitive (and chl to a lesser extent) and so is the aa & ee combination. And I think the 'smut' patterns (residual eumelanin) on A-ee? Is chd also temperature sensitive to any extent? I really haven't noticed any shading in the silver martens or chinchillas.

Leaving aside for the moment the question of the heterozygotes…

If both AAee and aaee show temperature sensitivity in the distribution of eumelanin (residual eumelanin smut in the AAee), but AAEE and aaEE do not - wouldn't it be more accurate to say that e is temperature sensitive rather than to say that a is? Granted, it has to do with the way the proteins produced by the two genes fit together, but isn't e the gene that is changing? (I thought it was the receptor which changed structure, which is coded by E/e). Or biochemically is it actually the product of the A-gene that changes structure in response to heat? If so, does the A-version (protein produce by the A-allele) change in the same way as the a-version?

Pointed aach- and martenized points AAch- (as well as at-ch-) both show temperature sensitivity as well. Color only develops after birth, when the points cool. Which leads us to saying that ch is temperature sensitive (not that a is temperature sensitive).
I think the same is true for chl (shaded and shaded-agouti both show similar temperature sensitivity in pattern) … only they usually have color right from birth, so the effect isn't as pronounced?

Back to the AaEe heterozygotes that show shading…

If e is temperature sensitive, but a is not … then the carried e is more likely to be involved in the residual shading (assuming a degree of codominance). I would expect AaEE to not show the shading.

On the red heterozygotes … Aaee
The carried a gene should not make any difference to the phenotype. And what you are showing in the photos isn't a difference in smut (black pigment at the tips) but a difference in the intensity of red (phaeomelanin or red/white balance). Highly likely that W is involved in this - or other modifiers intended to sharpen color and reduce smut on reds/torts. Normal agoutis are WW and reds ww … which makes the crosses Ww (which is co-dominant). I hadn't heard of W being temperature sensitive … but Ww is infamous for creating uneven color … leaving patches that have the narrower midband of agouti and patches that have a wider midband like the red (plus a lot of 'in-between'). Over the flanks of any rabbit, you tend to see more of the under color just because the movement of the leg bones shifting separates the fur - so if the red doesn't go all the way to the skin (as it should in a ww red with all the right modifiers) you get the visual effect of the flanks showing more under color. Any red that is WW or Ww is going to have a wider band of white or grey next to the skin - which will be more visible on the flanks.


Edited by NeuBunny, Jun 27 2015, 09:42 AM.
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reh
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Its this one: Posted Image
There you have the thermal image too and you can use this for sort of teaching :-)

Not ae is temperature sensitiv but e, which affects smut too (the agouti-yellow can not be darkened, but the ee yellow)
cchd eumelanin is as dark as C so there is no cold sensitivity. In case of cchm maybe yes.

Edited by reh, Jun 27 2015, 08:45 AM.
www.rabbitcolors.info - Images and Gene Codes
www.satinangora.de
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wildrabbits
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Reh its VERY important to distinguish what I am saying here..then you might understand better..by saying "tort pattern marking" I am ONLY referring to the specific shape of the marking itself on the side flanks and NOT a shaded or darkened effect!!! ONLY "a" makes this particular pattern on the side flanks of rabbits which can be hidden!!! The side flank "tort pattern markings" are actually lighter NOT darker for Aa rabbits.

Also just as I was describing my AaEej rabbit this one has the exact same side flank markings THAT ARE ONLY FROM THE a gene! The rabbit you showed Posted Image further confirms my thoughts as to whether Aa still shows without e just as I saw with my chocolate-chestnut harli carrying a.
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