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PostPosted: Tue Nov 24, 2009 7:57 pm 
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Asian Leopard Cat

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Thanks Elaine,

Very interesting - It has set a few questions churning in my mind - but the first one is if it's known if Schooners Salt Water Classic is/was AA or Aa?

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Tigra, Azlan, Bilbo and Zion


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PostPosted: Tue Nov 24, 2009 11:56 pm 
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Asian Leopard Cat

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It would be nice to know, but I think it is immaterial what she was as the input of the solid non-agouti gene could have come from anywhere. Although the ASH often gets blamed it needs two to tango.
Many cats and breeds were used originally and I am sure the Bengal breed has its fair share of oops matings too, some way back, others may be very recent. As non-agouti (a) is a recessive gene, it is possible it may have lain hidden for long enough. Also as melanistic kittens were secreted away and denied by many breeders then it is impossible to say exactly where it came from and to be able to map its descent accurately.

Because the Bengal is a "Dominant" breed then it tends to stamp its dominant traits onto anything it mates with, so I am sure there are "purebred" cats out there and in pedigrees who were sired by the local tom when the queen escaped, or by another breed that the breeder just happened to have at the time.
If that sire was solid then you get 100% solid carriers in the kittens Aa, if those cats never meet another solid carrier or never have DNA testing then it is never exposed, but can be passed on down the generations.

The blue/dilute gene is another recessive that may have a similar story to tell, same with the recessive longhair gene.

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PostPosted: Wed Nov 25, 2009 12:53 am 
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Asian Leopard Cat

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Indeed. To be honest the other questions burning in my mind are probably just as immaterial - not least becasue I'm not a breeder - but it does fascinate me.

Of course it does take 2 to tango, but if all silvers are coming from the same source, the same allele will populate the gene pool in multiple places from that one source and eventually meet again... Especially difficult to track if Agouti/non-agouti (A/a) and Inhibitor/non-inhibitor (I/i) are not linked, and also of course that I is dominant whilst a is recessive...

But back to the point that actually interests me, rather than that slight tangent....I'm particularly interested if it is understood why the markings on some cats is black down to the skin (ie no banding in the black areas) but banding still occurs in the non-black areas. From the information above on the genetics sticky it explains this banding (and hence the expression of a coat pattern) is controlled by the agouti gene, and it seems the pattern itself is determind by various alleles of the ticking gene, which is fine, but that doesn't explain the black expression which appears to me as 'non-agouti' in spots/markings, and 'Agouti' in other areas, compared to other cats which have banding all over- including in the spots...

Clearly it's not simple then.....but I can't help suspecting it is related to the regulation of these 2 agouti alleles. It could be polygenic or an epigenetic regulation, or linked to heterozygosity of Agouti Aa or another allele not yet mentioned, or a combination of factors. I just wondered if it was known or not? Makes all the difference in the ability to "lock it in" with selective breeding.

I just can't help suspecting (with no evidence other than a hunch) that the black expression seen in cool brown is linked to heterozygosity of the Agouti gene, and hence would correlate to the appearance of melanistics. In which case melanistics could also be they key to improved black expression...?

I guess the key question is what experience breeders have when trying this?

Anyway, just a few questions I was pondering - but it really doesn't affect me to know or not... as I said ultimately immaterial to me as I'm not a breeder - but something I would give a lot more thought to if I was...

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Tim and the Family Feline

Tigra, Azlan, Bilbo and Zion


Last edited by Thundercat on Wed Nov 25, 2009 1:14 am, edited 1 time in total.

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PostPosted: Wed Nov 25, 2009 1:07 am 
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Asian Leopard Cat

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Oooops - just re-read that, and don't want it to be misinterpreted as things so easily can online - and thought I'd better clarify that that last line isn't meant to imply what breeders should be thinking about, I'm certainly in no position to be saying that - just what I would be thinking if I were a breeder - but I'm a bit of a geek and get fascinated by some things that would make the average person slip into a coma :oops: :oops: :lol: :lol:

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PostPosted: Thu Nov 26, 2009 1:47 am 
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Asian Leopard Cat

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Thanks Karen (Suntouched) for adding some further clarification on this. Karen explained that her boy Merlin who has superb black expression has been genetically tested and definitely does not carry non-agouti (a). So that definitely answers my question.

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PostPosted: Thu Nov 26, 2009 5:54 pm 
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Asian Leopard Cat

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Quote:
Of course it does take 2 to tango, but if all silvers are coming from the same source, the same allele will populate the gene pool in multiple places from that one source and eventually meet again...

I am aware of that but Madeline's melanistics come from a sire line that has no ASH silver in it. Another "famous" UK melanistic Springmeadow Domino has the ASH silver only on the dam side of the pedigree too.

I was also going to quote the Merlin example too, regarding Aa and black expression.

Whether melanistics are the key may be tested more in the future as more of them are turning up, so questions may be answered. I personally feel that if your cats show black expression or have that in their ancestors then the progeny will echo that and the fact that you have used the melanistic kitten out of the litter makes not the slightest bit of difference to the result than had you chosen a spotted kitten out of the litter, unless you want to breed specifically for melanistics of course. The general traits that you get all depends on the mix that that particular kitten has inherited as opposed to the fact he is solid in colouration.
I also feel that had the parents of the melanistic kittens been poor specimens with faded coats then that is what I feel the progeny of the melanistics will end up as well. I could be wrong though, time will tell.

I think that the main colour genes are modified by so many factors and other genes so it is not often as simple as only one gene being involved in a desirable trait.

What I am interested in is how this degree of clarity can be achieved in a 10 year old cat.
Image
and
Image

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PostPosted: Thu Nov 26, 2009 11:36 pm 
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Asian Leopard Cat

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Yep, if the black expression we are seeing in SBTs is completely unrelated to Aa then melanistics are of no help whatsoever in that regard...unless of course they happen to also be carrying the factors which ARE responsible. I'm sure there are many many factors, I was just curious as to if that could be one of them.

It's fascinating for me learning all this. The Jaguar and Leopard are stunning and have quite amazing contrast. There is clearly something (be it genetic or epigenetic) regulating melanin secretion in these wild cats that has yet to be locked into the domestics, if it's not already there at SBT level, it will need to be introduced, and if so then the answer to your question will lie in the ALC.

I know this is not an option that many breeders (including yourself) choose to pursue, but it certainly is the source of the black expression in my new baby F2 boy and his sister Hazina that Karen now has, and thus goes back to the points Gaynor was raising in one of the other threads. The problem there is the sterility of EG males making it harder to carry it to SBT level, and having enough lines that carry it to be able to lock it in without inbreeding. Although as Gaynor said on another thread, there are also many EG lines which do not have strong black expression, which add nothing in this particular regard.

It's a shame that breeding is so empirical in most cases - but then again that is what must make it so fun and rewarding - I really see it as an art.

Thanks so much for taking the time to discuss it though Elaine. I could pick your brain for hours I'm sure, and if one day in the future I am able to start breeding I would be honoured to gain from your knowledge and experience as a mentor.

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Tim and the Family Feline

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 Post subject: genetics
PostPosted: Sun Nov 29, 2009 4:38 pm 
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Bengal Kitten

Joined: Sun Nov 29, 2009 4:08 pm
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genetics are very interesting but i have to confess they are also very confusing! :oops:
if i was to try to predict the colour/markings of a litter how would i do that?
for example if sire was blue eye snow spotted (with one parent blue eye snow marble and the other brown spotted) and dam was silver marble (parents blue eye snow spotted and silver spotted).

Sarah


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PostPosted: Sun Nov 29, 2009 5:01 pm 
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Asian Leopard Cat

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Quote:
Thanks so much for taking the time to discuss it though Elaine. I could pick your brain for hours I'm sure, and if one day in the future I am able to start breeding I would be honoured to gain from your knowledge and experience as a mentor.

I would be happy to help, Tim. :)

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 Post subject: Re: genetics
PostPosted: Sun Nov 29, 2009 7:50 pm 
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Asian Leopard Cat

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Location: south east england
itwouldberudenot2 wrote:
genetics are very interesting but i have to confess they are also very confusing! :oops:
if i was to try to predict the colour/markings of a litter how would i do that?
for example if sire was blue eye snow spotted (with one parent blue eye snow marble and the other brown spotted) and dam was silver marble (parents blue eye snow spotted and silver spotted).

Sarah


Hi, welcome to the forum :D .
Snow is recessive, so the sire can only pass on the snow gene.
Silver is genetically brown, just with the colour inhibited. The dam will have snow genetics inherited from her one parent & brown from the other. As she herself is silver, she can pass that to the offspring.
In the litter you will have a possibility of snow, brown & silver & possibly also silver snow.


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PostPosted: Sun Nov 29, 2009 8:51 pm 
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Bengal Kitten

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thanks for your reply that really helps, although i think it will take me some time to get my head fully around genetics, but i will keep trying!


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PostPosted: Sun Nov 29, 2009 9:22 pm 
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Asian Leopard Cat

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Don't worry I think we are always all still learning! It's good that you are interested & want to know more :wink:
Why don't you start a thread in the introduction section to introduce yourself & your cats, so that everybody can welcome you as not everybody reads the breeding section :D


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PostPosted: Tue Dec 01, 2009 5:04 pm 
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Asian Leopard Cat

Joined: Fri Aug 24, 2007 3:43 pm
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Location: France (Dijon)
For Thundercat... Not sure that will answer your question but here's a translation of the detailed explanation about the agouti hair ;)

Quote:
The color of hair and skin is due to pigments, melanin(e?)s
There are 2 variants, eumelanine, black, and phaeomelanine, yellow-orange.

The agouti gene (A) codes for a protein, the agouti protein, which, when in a sufficient concentration, inhibates the production of eumelanine when the hair is growing.

The agouti protein acts as a stopper (er... the on/off button to shut the light ? :lol: ) on the production of the black pigment, eumelanine.

So, if you look closely at an agouti hair, you can "retrace its history" from the tip...

Image

1. When the hair begins to grow, eumelanine is abundantly produced : the hair tip is jet black
2. When there's enough produced, the agouti protein acts as a stopper. No more eumelanine is produced. Cells then produce the closest thing they can : phaeomelanine.
Because the agouti protein also has a slight inhibitor effect on it, it's more yellow than orange.
3. All the agouti protein is used, eumelanine is produced again (and the agouti protein too...)
4. There's again enough agouti protein, back to phaeomelanine production

So you get an alternance of black eumelanine strips and yellow-orange phaeomelanine :

Image

Which the human eye sees as brown.

Some more explanations for the more curious...

At the melanocytes surface (cells that produce the pigments), you can find a lot of receptors. Some of them, melanocortine receptors (MC1-R), can accept 2 molecules which are then in competition :
- the melanostimulin hormone (α-MSH)
- the agouti protein

When the melanostimulin gets in the receptors, eumelanin is synthetised as the pigment because of an enzymatic chain reaction that the α-MSH fixation on the receptors begun.

When the hair starts growing, the protein agouti is synthetised in the hair follicule. When its concentration is high enough, there's a balance that gets in its favor and it takes the place of the MSH in the receptors.

But as it doesn't activate the enzyms necessaries for the production of eumelamine, phaeomelanine gets produced instead because there's a componant missing (I know you'll get what I mean, but for others, imagine that molecules are complex puzzles : phaeomelanine is like eumelanine with a part missing, because of the agouti protein and the broken enzymatic chain reaction, that part doesn't get attached to the molecule so you get phaeo instead of eumelanine...)

So an agouti hair is the result of the competition between 2 proteins, the agouti protein and the MSH that "fight" to get in the MC1-R receptor ;).

That goes without saying, but it's better when you say it, many actors (proteins) means many genes to produce them, and particular relations between those different agents.

Their "competitivity", their "concentration", their "selective affinities" are not the same in each individual... from one cat to another, agouti hairs are not identical !
Width of stripes of phaeo and eumelanine can vary (greater "affinity" of the receptors to the agouti protein or the MSH, variations of concentrations...) as the "clarity" of the transitions.


Sorry if some words are too literally translated from french, hope that's understandable :lol:

It doesn't really answer your question but maybe you could draw conclusions... ;)

But I personally thing that any ticking in supposedly black hair is more probably the result of the action of polygenes than of the agouti gene.

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PostPosted: Wed Dec 02, 2009 3:54 am 
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Asian Leopard Cat

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Hi Ann,

Many thanks for that. I really appreciate the translation, it made sense. Well it does explain how the agouti protein is involved in regulation of banding. Interesting that agouti and MSH are in competition for MC1-R, as analogues they'll be from the same gene family, which certainly lends itself to a range of polygenes. I'm assuming given the range of coat colours that Eumelanin and Phaeomelanin are not the only 2 pigments involved, I can see how this could quickly become quite complex.

But it does still leave me with my question (which is effectively the same/similar as Elaine's key question) unanswered. It seems as though something could potentially be upregulating expression of melanostimulin (or more ultimately expression/translation of eumelanin as I guess it could even be due to another pathway) in certain cells, causing some hairs to grow completely black, whereas others remain banded.

It's very intriguing as when I look at my cats 3 of them (2 SBT Bengals and a Blue Tabby Maine Coon) have clear banding that means their pattern is essentially superficial - part their fur at even their darkest point and the lighter undercoat is the same light colour as it is everywhere else, whereas the F2 boy is quite different. His black markings really are full length black hairs, part his fur where he is black, and it's black down to the skin. If I were to shave his fur the stubble would still be spotty! I find it really quite fascinating (small things eh) as its suddenly very obvious that I have not ever seen it before on any cat. (maybe I just haven't lived?? :oops: :lol: :lol: )

Even without understanding the mechanism, it could be very interesting to start identifying which cats have this feature, and seeing how reproducible it is if lines are strategically bred.

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Tim and the Family Feline

Tigra, Azlan, Bilbo and Zion


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PostPosted: Wed Dec 02, 2009 6:48 pm 
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Asian Leopard Cat

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Location: south east england
Thundercat wrote:
whereas the F2 boy is quite different. His black markings really are full length black hairs, part his fur where he is black, and it's black down to the skin. If I were to shave his fur the stubble would still be spotty!


Like this....
Image

Image

2 of my little ladies (SBT) who were neutered last week. I love those black-to-the-skin markings! :D


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