How to make a chocolate dog

I had a request to write about the chocolate color in Labradors. It seems appropriate since today is Easter.

Genetically, chocolate is the rarest of the Labrador coat colors. This is because there are only 2 ways the genes combine to produce Chocolate dogs. Chocolate is a recessive coat color. It is signified by the b gene. To produce a chocolate you must have two b genes and at least one E gene.

One of the basics in breeding is that a puppy will get 1/2 its genes from one parent and 1/2 from the other parent. Chocolate coat color is a simple autosomal recessive trait in Labradors. It is recessive to black which means that even though one can't see the chocolate color, it is still there in the genetic make-up of the dog. Black is a dominant trait in Labradors and will express itself over the chocolate gene.

So let's take the following example:
A black Lab with no chocolate gene is a BB, while a black Lab that carries the chocolate gene as a recessive trait is Bb, and a pure chocolate Lab is a bb. Now to complicate things a bit, there is a third color, yellow. Yellow is produced by the presence of a recessive gene that can blot out the expression of black or chocolate. So EE indicates that no yellow gene is present while Ee is a yellow carrier that can appear either black or chocolate and ee is a yellow lab.

There are 81 different combinations that can produce coat color in Labradors. There are a couple of sites that provide color combination probabilities. One is the Wing n' Wave site at http://www.labbies.com/genetics.htm
And the other is at http://users.tpg.com.au/choclab/cci/genechoc.htm

Happy Easter to all.