In Labrador retriever breed of dogs, coat colour is determined by several genes.

Question

In Labrador retriever breed of dogs, coat colour is determined by several genes. One gene determines the black or chocolate coat colour, with the black colour (B) dominant over chocolate (b). Your neighbour owns two Labradors from the same litter, both female, one black, one chocolate and he paid 5000 dollars to send his black Labrador female to breed with a champion black Labrador owned by a disreputable character. He is not a witness to the mating. Last weekend the neighbour’s dog gave birth to 12 puppies, 7 of which are chocolate colour. What are the most likely and the second most likely explanation for this?

Explanation / Answer

Answer:

The coat color of Labrador Retrievers (Black, chocolate, or yellow) is controlled by two different genes. The first gene controls the color of the coat, and is either B=Black or b=chocolate. Each parent provides the offspring with either a "B" gene or a "b" gene. Black is dominant over chocoloate. This means if either gene from the parent is "B," the offspring's genetic code for coat color will be Black. The genetic combinations include:

BB = both parents provide a Black gene

Bb = mother supplies Black, father supplies chocolate; or mother supplies brown, father supplies Black

bb = both parents provide a chocolate gene

An offspring with one or two "B's" will have a Black nose; one with two "b's" would have a chocolate nose.

Little eee genes are able to influence or in certain cases to ‘switch off’ the ‘bee’ genes that cause black and chocolate coats. Each dog inherits two ‘eee’ genes, one from each parent. There are two types of ‘eee’ gene.

One we call big E (this is the dominant gene) and it does not interfere with the ‘bee’ gene
And one we call little e (this is the recessive gene) and it has the potential to mask or ‘switch off’ the ‘bee’ gene that would otherwise give us black or chocolate coats. The result is a yellow dog

This situation satetes that the mating of the black labrador was done with a choclate labrador.Possibly the black labrador which he had was of EEBb and it was mated with Eebb choclate labrador.So that EEbb and Eebb genotypes have been produced so out of 2 , 7 puppies were chocolate in colour.

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