Have you ever looked at a litter of Labradors and wondered what determines what color the puppies are? It’s possible for two black Labs to produce an entire litter of yellow puppies or chocolate puppies. Yet, two yellow Labrador Retrievers bred together will only ever produce yellow puppies. Color genetics can be a fascinating subject. For those interested in breeding or desiring a specific color of Lab, understanding the genetics behind color will make it easier to predict what color puppies will be in the litter.
Black vs Chocolate
Color is determined by basic autosomal recessive and dominant gene inheritance. This means that the color genes are not linked to the sex of the dog and that factors like incomplete dominance do not come into play. It is determinable because it is not governed by a number of different genes located at different points on the loci. An example of the latter is hip dysplasia. It is governed by several genes and further complicated by environmental factors, all of which makes it very difficult to predict with complete accuracy whether or not a dog will develop hip dysplasia based strictly on his parentage.
There are two loci (gene locations) involved in color in Labradors. The first determines black or chocolate coloration. The black gene (B) is dominant to the chocolate gene (b.) Each dog inherits a gene from each of his parents. So a dog that inherits a black gene (B) from one parent and a chocolate gene (b) from one parent is described as Bb. He is black in appearance although he does carry a chocolate gene and, if bred to another dog that carries the chocolate gene, can produce chocolate puppies. A dog that is BB (so he has two black genes, one from each parent) cannot produce chocolate puppies even if bred to a chocolate dog because his offspring cannot inherit a chocolate gene from him. A chocolate dog is bb and can only give his offspring the chocolate gene at this loci.
BB – black in appearance and can only give the black gene to his offspring
Bb – black in appearance and can give a black or chocolate gene to his offspring
bb – chocolate in appearance and can only give his offspring a chocolate gene
The determination for yellow is at a different loci and is determined by a different gene. In order to be yellow, a dog must have two copies of the yellow gene (y means that the yellow gene is present and Y means that it is absent) at this loci. If that is the case, it does not matter what is present at the black/chocolate loci, the dog will be yellow. So a yellow dog is always yy at the yellow loci. A black of chocolate dog is always Yy or YY at the yellow loci.
Because a yellow Labrador can only contribute the y gene to his offspring, two yellows bred together can only produce yellow puppies. Black and chocolate dogs can both carry the y gene and produce yellow puppies if bred to another dog that carries the y gene.