Colours of the Rainbow

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Colours of the Rainbow

Post  Admin on Tue Feb 19, 2008 12:36 am

So, you have your ribbons, you have one Sheltie, and you need to know how to get that colour you want.

Here's where things get tricky.

Welcome to Sheltie Colour Genetics 101

1. Base colours

There are three base colour in Shelties - Sable (S), Tricolour (T) (black white and tan), and Bicolour (b) (black and white). A Sheltie will carry two alleles of these genes to form its base colour.

Sable is codominant to both tricolour and bicolour. This means that a dog with one Sable (S) gene will always be a brown colour, ranging from golden to mahogany, but if that same dog also carries a black gene, it will tend to be darker than one carrying two sable genes.

Sables with two sable genes are called "pure for sable" and when bred, will only produce sable base colours.
Sables carrying one sable gene and one tri gene (T) are called tri-factored sables, and when bred, could produce sables or tri base colours.
Sables carrying one sable gene and one bi gene (b) are called bi-factored sables and when bred, can produce sables, tris, and bicolour base colours.

Tricolour is dominant to bicolour. That means that if a dog carries one tri gene and one bicolour gene it will be tricoloured.

A tri with two tricolour genes is called simply a tricolour, and can produce sables or tris.
A tri with one tri gene and one bicolour gene is called a bi-factored tris, and can produce all three base colours.

A bicolour will always have two bicolour genes, and when bred, can produce all three base colours.

Base colour gene combinations

Pure for Sable [ SS ]
Tri-factored sable [ ST ]
Bi-factored sable [ Sb ]
Tricolour [ TT ]
Bi-factored tri [ Tb ]
Bicolour [ bb ]

Example breeding for base colours
Tri-factored sable x Bi-factored tricolour
[ ST ] x [ Tb ]

Punnett Square (just like PI!)
| T | b
S | ST | Sb
T | TT | Tb

So this breeding would produce trifactored sables, bifactored sables, tricolours, and bifactored tricolours

2. Merles


The merling gene is essentially a dilution gene. Each copy of the dilutes the base colour of the coat (usually unevenly, giving darker "merling" spots on the body which indicate the dog is a merle).

This means a sable becomes a lighter sable merle (and can be tri or bi factored), a tricolour becomes a blue merle (and can be bifactored) and a bicolour becomes a bi-blue merle.

Breeding merles can be tricky, so pay close attention.

Merling is considered an autosomal dominant trait with additive properties. That is, the more copies of the gene you have, the greater the effect on the puppy.

Copies of the merle gene are represented by [ M ] while nonmerle gene is represented by [ m ]

A "normal" merle has ONE copy of the merle gene [ Mm ], a nonmerle has NONE [ mm ] and a double merle has TWO [ MM ].

Non-merle bred to non-merle CANNOT produce merle.

A normal merle bred to a non-merle will have a fifty percent chance of producing either merle or non merle.

A normal merle bred to a normal merle has a twenty five percent chance of producing a non-merle, a fifty percent chance of producing a normal merle, and a twenty-five percent chance of producing a double merle.\

A double merle bred to a non-merle will produce all normal merles.

A double merle bred to a normal merle will produce fifty percent normal merles and fifty percent double merles.

Double merle to double merle will produce only double merles.

**A Note About Double Merles**
Double merles in RL are often prone to health problems, including blindness or deafness, and so many breeders avoid producing them. You are permitted to breed two merled Shelties together, but you may produce a double merle by doing so. If that double merle has white ears AND/OR white over both eyes and blue eyes, it will be considered unworthy of being breeding quality and you will be unable to breed it in the future.

3. White factoring

White factoring works essentially the same way as merling, except that a dog with two copies of the white gene will have a white body and coloured head, but none of the health problems associated with double merles.

A non-white factored dog is [ ww ]
A white factored dog is [ Ww ]
A colour headed white is [ WW ]

White factoring is usually visible by white on the stifle (the curved part of the back leg) although it may be impossible to tell without breeding sometimes.

Non-white to non-white produces only non-white factored dogs.
White factored to non-white factored will produces fifty percent each of white factored and non white factored
White factored to white factored will produce 25% non-white factored, 50% white factored, and 25% colour headed white
Colour headed white to non white factored produces all white factored
Colour headed white to white factored produces 50% each of white factored and colour headed white
Colour headed white to Colour headed white produces only colour headed white!

And that's it! Easy as pie right?

OK, maybe not..... but there will be a thread below to ask questions if you don't understand!

Have fun


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