Whats in a colour?

Welcome to this weeks edition of the ADNZT dog blog.

Last week we looked at some of the aspects taken into consideration when choosing potential parents for our litters and answered the first of two questions…..‘How are the parents of puppies selected’.

This week we’re still looking at the puppies. We have had two litters recently, both with specially selected parents. Both sets of parents were different colours.

First, there was Asher and Poppy with the ‘H’ litter.

Then there was Fonzie and Ruby with the ‘K’ litter.

So, our second question that we look into this week, is ‘What determines the colour of the pups?’

Personally, I find colours in the dog world very interesting. First of all you have the terminology. Retrievers can be Black, Chocolate (Liver) or Yellow. But a Golden Retriever is not referred to as yellow. They are always called Golden Retrievers, even when that colour range can vary quite considerably. Whilst rarer, there are also Black Retrievers and Chocolate.

So, without getting too technical about it, let’s explore what determines the colours of these pups. I have to make a disclaimer here – I’m not a genetic scientist, so I have researched this week and mixed that research with my observations and high school biology classes :-). It’s fascinating stuff!!

We all know that our genetics are made up from a gene pool held in our DNA. We see similarities within ourselves to our parents, and it’s the same when we look at the puppies and their parents.

Each point along the DNA strand is called a ‘Locus’. (The plural for Locus is ‘Locii’).  Locii are referred to by using letters to denote them, and there are a whole range of them that effect the DNA, but only three of them refer to the colour of a Labrador –  B, E and K.

Within these locii are two ‘Alleles’, one from each parent. The Alleles can be either dominant or recessive. For ease of explanation, the dominant allele as an upper case letter, and the recessive as a lower case letter.

The ‘K’ locus refers to the solidity of the colour. Because we never get multicoloured purebred Labradors or Retrievers, we know that this locus is ‘KK’ – i.e. two solid colouring alleles.  All purebred Labradors and Golden Retrievers are a solid colour because this locus has been kept true as ‘KK’ throughout the lines. I guess this ‘K’ locus would come into play if we were talking about Spaniels or Huntaways, where there can be a mixture of colours in the dogs coat, but for our purposes we can take the ‘K’ locus out of the equation.

The ‘B’ locusrefers to ‘Black’ vs. ‘Liver’. But not necessarily the coat colour. More the pigmentation colour. If a locus has two BB alleles, or is Bb (one dominant and one recessive), then dominance wins, and the black comes through.

If, on the other hand the locus is made up of two recessive alleles ‘bb’, (as seen in the bottom right hand box on this table), then the outcome would be liver coloured, or brown. But this may only show in their skin pigmentation, such as their nose colour.

So…hang on a minute…..Ruby and Asher aren’t brown or liver coloured, so what’s happening there?

That’s where the ‘E’ locus comes into play. If ‘E’ is dominant, then it has no effect on the outcome of the colours. So if the puppy receives an allele from each parent that makes up either ‘EE’ or ‘Ee’, then the black will come through. If, however, the puppy receives two alleles that means it is ‘ee’, then it effectively means they do not produce eumelanin in the coat. This means that they are unable to produce black or liver hairs, so they are yellow instead.

So, we now know that all Golden Retrievers and Yellow Labradors have to be ‘ee’ on that particular locus. As parents, they will therefore be donating one ‘e’ to the mix of their puppies. If the other parent also has an ‘e’ in their make-up, then the result will be a yellow pup. The table below shows some different combinations. Remember, that if there is a dominant ‘E’, then that will bring through the black, but two ‘e’s mean yellow.

From this we can deduce that whilst Ruby (K litter dam) must be ‘ee’, Fonzie (K litter sire), must be ‘Ee’, therefore meaning he is black, but carrying the recessive allele that has passed on to some of his pups, making them yellow. Without a recessive allele from Fonzie, there would only be dominant ones, so all the pups would have been black.

When we look at Asher and Poppy, we know Asher is also ‘ee’, as he’s a Golden Retriever, but Poppy must therefore be ‘EE’, as all her pups so far have been black. However, her pups would carry the recessive ‘e’ allele, so if they were mated with another ‘Ee’ or ‘ee’, then we might see yellow pups from that union.

One locus that we haven’t talked about is the C locus, which affects the shade of a golden retriever. But we won’t delve into that this week!

I hope all this makes sense to you. My thanks to Doggenetics.co.uk for their help in compiling this blog.

Many thanks for reading. Please leave a comment, as it all helps to raise awareness.

Have a great week.