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Author Topic : Colour Genetics in ShowDog (Re-Posting)
 gaylanstudio
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7/1/2018 10:43:31 AM reply with quote send message to gaylanstudio Object to Post   

I put this together shortly after our colours were added and have updated it. I am re-posting it, partly to keep any new-comers informed and to keep it from getting lost.

A quickie genetics course:

English Cocker colours in ShowDog are fairly simple. There are 5 loci involved - A, B, E, R, and S. The American Cocker has included the K Locus which makes it somewhat more complicated. In reality the colours of the two breeds are pretty much the same although the frequency of occurrence of certain colours is different.

The term Locus (Loci is the plural form) simply refers to a particular spot in the DNA chain. The individual genes occur in pairs - one comes from the sire, the other from the dam. Depending on the locus there are (in the EC world of ShowDog) two possible forms of each gene - these forms are called "alleles".

The alleles of the A Locus are represented as A and at. We use upper case to indicate the more dominant form. When I write "A/at" this says that this dog inherited the dominant A from one parent and the recessive at from the other - we do not know which came from which. The other possible combinations are A/A and at/at.

The alleles of the other loci are B/b, E/e, R/r, and S/sp.

The S Locus determines "White Spotting" - whether the dog is solid or particolour. S is the dominant allele; sp is the recessive and produces the particolour pattern. S/S, and S/sp will both be solid. sp/sp will be particoloured.

The R Locus carries the roan gene. R is dominant and produces the roan pattern, however the roaning will only be visible if the dog has significant white areas - i.e. it is an sp/sp particolour. An r/r, sp/sp will be a clear white particolour; an R/r,sp/sp and an R/R,sp/sp will be roans. The Roan is dominant but its presence will be hidden by the dominant S.

The coloured areas of a particolour are determined by the other loci.

The recessive e lacks the ability to produce dark pigment - black and brown, or liver as it's called in EC's. Therefore a dog that is e/e will be some shade of red/yellow. It will be solid red if has a dominant S; it will be orange or lemon if it is sp/sp.

The A Locus determines the pattern of the dark pigment - i.e. black or black and tan (tri-colour if it's a parti). Remember though that e/e prevents dark pigment so an e/e dog will be red/orange regardless of A. The tan point pattern is recessive - at/at will have tan points, A/at, and A/A will not have tan points. The A/at has the potential to produce tan points if it is bred to another carrier of the at allele.

The last locus is B and it affects the type of dark pigment. B/B, and B/b will be black - solid black, black and tan, black and white, black,tan and white. The recessive b/b will change the black to brown/liver. B/b will be black but can produce liver. The terms Lemon roan and Lemon and white are used when b/b and e/e and sp/sp occur together. The recessive b, while normally associated with turning black to brown also has a diluting effect on red. The “B” status for solid red dogs is indicated as Red(liver) or Red(black). Red(liver) is e/e,b/b,S/?. Red(black) is e/e,B/?,S/?. The b/b red will have a brown nose, eyerims, and a somewhat lighter coat colour than the B/? red.


You can play a little game. Get a piece of paper or light weight cardboard (file cards works well) and a red and a blue pen then cut out ten equal squares, dividing them into two piles of 5.

With the blue pen write "A" on one side of a square and "at" on the other. Write a "B" and "b" on either side of another square, then "E" and "e", "R' and "r", and "S" and "sp". Do the same with the other 5 squares using the red pen. The blue squares represent the genes of the sire; the red squares are the dam.

Now put all 10 squares into a cup, shake'em up and dump them out on the table. Without turning them over pair them up alphabetically - a blue A with a red A, a blue B with a red B, and so on.

On a sheet of paper, record the results. Put all the squares back in the cup, shake, dump, sort and record again until you have four sets of results. They should look something like this:

A B E R S
at B e r sp

A B e R sp
at b e R sp

A b E R S
A b e r S

at B E r S
at b E r sp


You have just "bred" a litter of four paper puppies. The first one will be solid black, the second will be an orange roan, third solid liver, and the forth will be black and tan.

The sire and dam are both solid black but, by design they each carry the dominant and recessive allele for each locus so theoretically they could produce any EC colour under the ShowDog sun. They are A/at, B/b, E/e, R/r, S/sp

This basically is how the genes are mixed up and rearranged to produce each new puppy.

You can add the sex to this little game by taking two more squares and putting a red "X" on both sides of one, and on the other a blue "X" one side and a blue "Y" on the other. These will represent the XY chromosome. A red X and a blue X means a girl, a blue Y with a red X is a boy puppy.

"Breed" another litter - you can make bigger or smaller litters if you like but four works well. Then you can go another step and make squares for two of the puppies that you produced - for example puppy one above would have squares with A/at, B/B, E/e, R/r, S/sp - write them in blue if its a male, red if its to be a female. Then "breed" the puppies together.
 GaylanStudio9
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9/28/2018 9:14:30 PM reply with quote send message to GaylanStudio9 Object to Post

Bump.
 gaylanstudio
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12/14/2018 8:53:51 PM reply with quote send message to gaylanstudio Object to Post

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 gaylanstudio
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3/19/2019 11:41:24 AM reply with quote send message to gaylanstudio Object to Post

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 gaylanstudio
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5/25/2019 10:51:42 PM reply with quote send message to gaylanstudio Object to Post

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 gaylanstudio
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9/2/2019 1:37:49 PM reply with quote send message to gaylanstudio Object to Post

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 gaylanstudio
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1/5/2020 8:39:32 PM reply with quote send message to gaylanstudio Object to Post

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 PicketFence Kennels
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1/7/2020 12:13:34 PM reply with quote send message to PicketFence Kennels Object to Post

This is great information! Thank you for posting!
 Tarot
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1/10/2020 11:24:17 AM reply with quote send message to Tarot Object to Post

Gaylanstudio, if I wanted to try for black in Shih Tzus how would I go about that? I have never seen one on the site. How do I know if it's a recessive color (I assume it is since there aren't any)? Where do I even start, or should I?
 DoggyPanache
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1/10/2020 11:24:58 AM reply with quote send message to DoggyPanache Object to Post

Sorry, meant to post from this kennel.
 DoggyPanache
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1/10/2020 7:26:36 PM reply with quote send message to DoggyPanache Object to Post

I found the link at the bottom of the page and bought a little black Shih Tzu just like my Emerald's Lily Rose of Tarot, my RL girl.
 gaylanstudio
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1/23/2020 12:19:54 AM reply with quote send message to gaylanstudio Object to Post

I just took a quick look and it does look like black is dominant.

You have to think about it as two parts though - the white pattern - the white is recessive S,si,sp,sw where S is the dominant and will produce no white, which is what you seem to be after. (Note - I'm not sure the breed carries all these off hand.)

So, if you have a solid red/sable, whatever and a black and white parti, you have the fixings for a solid black.

I didn't look too much at the specific colours in the breed but black and sable I know, brindle maybe to.
 gaylanstudio
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3/7/2020 10:35:03 AM reply with quote send message to gaylanstudio Object to Post

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 gaylanstudio
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4/23/2020 9:15:41 PM reply with quote send message to gaylanstudio Object to Post

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 GaylanStudio9
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6/10/2020 10:12:56 PM reply with quote send message to GaylanStudio9 Object to Post

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 gaylanstudio
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7/5/2020 11:02:46 PM reply with quote send message to gaylanstudio Object to Post

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 gaylanstudio
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8/9/2020 3:51:48 PM reply with quote send message to gaylanstudio Object to Post

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