Genetics in relation to coat colours

[Scarlett]

After following a lot of posts to do with breeding schnauzers and trying to predict coat colours, and what with being a science type with a fair bit of knowledge of basic genetics, I had a bit of a look into this. I had mentioned a while ago about trying to simplify this and explain it in, well, lay-man’s terms I guess, so that those who breed, or are just generally interested might better understand it. Please bear in mind this is built up firstly from my own knowledge of basic genetics, and what I have read from studies of coat colour and what is believed currently to be the case. This is by no means 100% fact as it appears this is still an area under a lot of study and as it is better understood by the experts things may change. However, I thought I could pass on a bit of wisdom to help people better understand some of this really complicated stuff. Enjoy, and apologies that it took me so damn long to do this (I promised this about 9 months ago and then got swamped with work).

If anyone has any further questions then feel free to PM me. I don’t get online as much as I used to but I will try and reply if I can. Chances are this will spread over more than one post so I’ve typed it up separately so that hopefully I can post all the sections together to make it easier to follow.

(question) Genetics for dummies (question)

Ok so to begin with I’m just going to try and explain as simply as I can the basic principles of genetics – it gets a lot more complicated when actually looking into schnauzer coat colours as there are lots of interactions of various different genes resulting in the final coat colouring but you need to understand this bit first, to make sense of the rest.

So class, sit up straight, eyes to the front, and pay attention (can you tell I work as a teacher!!)
(giggle)


* * * * *

Right so here’s a couple of basic principles to start with. Every characteristic is determined by a particular gene (a teeny weeny section of DNA) on each DNA strand. Each gene will have at least 2 forms called alleles and you will have 2 alleles, one you get from mum and one you get from dad. Some alleles may be dominant (i.e. they will mask the effect of the other allele), some may be recessive (i.e. they will only be shown if you have 2, otherwise it will be hidden by a dominant allele) and in some instances they can be co-dominant which means a mixture of the two is observed.

To put it into context – if a black is dominant and a white is recessive, black + white = black (the white is masked), if black and white are co-dominant then black + white = grey (a mixture of the two is shown). Generally most alleles are either dominant or recessive, co-dominance is less common but as an example AB blood group is a result of co-dominant alleles for A and B blood groups.

So now we’ve got that outlined, time to get a bit more complicated – again I’ll try and keep it as simple as I can for the time being so bear in mind this is just to give you an idea of how this works, I’ll come onto how this actually seems to work in terms of actual dog coats further on.

Now for the time being I’m going to stick with coat colour either being black or white, black being the dominant allele (denoted B) and white being the recessive allele (denoted w).

If both mum and dad are true black coated dogs, they will both have 2 copes of the B allele. As a result during mating all puppies will get a B from mum and a B from dad. These pups will then all be true blacks also.

Likewise if mum and dad are both white, all pups will be white, since the parents will have 2 copies of the w allele.

If one parent is true black BB, and one parent is white ww, then all puppies will be black but carry the white allele.

However, this gets more complicated if one or both dogs are black Bw (i.e. they are black coated due to the dominant black allele but also carry a white allele). In this case there are three possibilities:

If one dog (e.g. mum) is true black BB and the other (e.g. dad) is black Bw: puppies will all get a B allele from mum, but could get either the B or the w allele from dad. So although all puppies would be black in colour, there’s a 50:50 chance that they might carry the white allele.

If one dog (e.g. mum) is white ww, and the other (e.g. dad) is black Bw: puppies will all get a white allele w from mum and as before they could get either a B or a w from dad. In this instance this means there’s a 50:50 chance of a white pup (it gets a w from mum and a w from dad), or it could be black and carrying the white allele (w from mum and B from dad, remember with B being dominant it masks the effect of the white allele.

Finally if both dogs are Bw: pups could get a B allele from mum and dad and be true black BB, they could get a B from one and a w from the other resulting in black (but carrying the white), or they could get w from both parents and be white (the actual probabilities are 25% true black BB, 50% Bw black, and 25% white).

Please bear in mind this doesn’t mean that in a little of 4 puppies you’d get 1 BB black, 2 Bw black, and 1 ww white. This is the probability for *each* puppy, i.e. each individual pup has a 25% chance of being BB black, or ww white, and a 50% chance of being Bw black.

This hiding of a recessive allele explains why sometimes some odd/unexpected colours might appear in a fairly predicted mating, and colours can skip generations. In humans this is most noticed with ginger/red hair. Ginger/red is recessive, so is there were ginger/red haired people in the family, you could carry the gene for it, even if you aren’t ginger and it could reappear further down the genetic line.

Ok so how many have I lost now……here’s hoping not too many cause this is where it gets more complicated…. Eeep! (confused)

[Scarlett]

In reality these interactions between the alleles are far more complicated, mainly because coat colour isn’t controlled by one gene, there are lots of different genes, with their own alleles, for different aspects of the coat colour and make up.

Each gene is located on a certain point on the DNA strand, these points are called loci (or one locus). The locus of a gene is very specific to what is codes for, i.e. the gene which codes for eye colour in a schnauzer will always be at the same point on the DNA strand for any schnauzer – to attempt to simplify this each loci for a gene is given a letter of the alphabet so when you read something that starts going on about loci k for example this would relate to a gene for a specific aspect of the coat e.g. the banding in a pepper and salt coat.

I’d also like to mention at this point a bit about *why* the different colours appear. Each gene is a section of DNA which will trigger the production of a certain pigment in the body, the more pigment produced the stronger/darker the colour, and the mixture of these pigments produces the overall colour. In albino dogs, no pigments are produced at all for any part of the body which is why the coat will be absent of colour (white) and everywhere else will be pinky (and also why such animals must be kept out of the sun as they cannot produce the melanin pigment that helps protect the skin – what causes us to go brown).

Now schnauzer coats are complex things and are actually a result of various different genes at different loci in the DNA, each one linked to a certain characteristic, and it is the overall result of all these interactions which results in such effects as the banded pepper and salt coat, and the lighter muzzle etc on a black and silver and so on.

Going on what I have read so far this is just a quick outline of the various different genes which interact and have an effect on your pooch’s lovely coat:

Base colour: essentially the underlying colour of the dog, most noticeable in areas such as the nose. This is usually black or brown, black being dominant over the brown. This might not be so obvious in schnauzers as I think they generally all have black bases over here but in America where there’s a bigger range in colours you may notice this more – you often see it in Labrador’s, those with a black nose have a black base, those with a brown nose have a brown base.

Agouti: results in a banding effect of the hairs – some animals such as rabbits are termed agouti when they have that banded grey/fawn coat colour. This is most likely responsible for the pepper/salt colour which also displays the same banding in the coat.

Bi-colour: results in the two-colour effect seen in many dogs where certain areas e.g. muzzle/chest/paws are a differing colour to the body. This is usually black and tan, as seen in many dogs such as Rottweiler’s, Dobermann’s, GSD etc. This is only partly responsible for the black and silver effect as another gene comes into play also.

Chinchilla: causes the fading of the tan/bi-colour gene to a paler silvery colour and is fairly unique to schnauzers apparently. The degree of silvering can vary which is why some BS may have very silvery grey points, while some may be almost white.

I know someone also has mentioned about parti-colours and again this is triggered by another gene. In this instance it seems this gene can ‘switch off’ another, and this often only happens in certain areas rather than all over e.g. in a liver/white dog: the liver areas are a result of the gene for a liver coat, but in the white areas the parti-gene has ‘switched-off’ the liver gene resulting in no colour (i.e. white).

There is a dilution gene, which seems to be linked in with fading the colour of the coat. This would be apparent from birth it would appear but I do wonder if something to do with this gene could be the reason why some of you have got black or black/silver dogs that have faded as they have got older. This is only speculation on my part though. It also appears that there may be a gene at another locus linked to greying so again this might be linked with the fading colours of some black/black silvers.

* * * * *

So hopefully if you did manage to follow that firstly well done you (it took me a good while to get my head round it and I understood the basics already), and secondly you’ll have a better idea of just how complicated trying to predict and breed for particular colours really is. Although you can select certain individuals to breed together in the hope of getting certain coats in the pups, it’s damn near impossible to predict without at the very least knowing the exact genetic outline or both mum and dad (and even then there’s a lot of random elements to it also). Hence why someone could, say as in Jools case I seem to remember, breed 2 black and silver dogs, and end up with all pepper and salt.

Of course if any of you breeders want to offer a substantial discount on a couple of pups as thanks – all offers would be considered when I eventually come to get a puppy…..hee hee (hey you can’t knock me for trying!!) (sleazy)

For any further details I had a good read of the following websites and figured this all out from there. Enjoy:

http://abnormality.purpleflowers.net/ge ... albino.htm
http://www.schnauzerlover.com/articles/ ... olors.html
http://www.initiative-wms.com/DNA.htm
http://abnormality.purpleflowers.net/genetics/index.htm
http://bowlingsite.mcf.com/genetics/genetics.html

There’s plenty more sites around too so plenty to keep people occupied! (nerd)

[Eddie]

That's a very informative post and would be very helpful for anyone who is currently breeding or considering breeding.
I have made it a "Sticky" so it will remain as the first thread in the breeding section.

[Mitch]

Scarlette a very interesting post Thank you (bigthumbs)

[Scarlett]

well I'm glad to be of service, I just hope people can make sense of it. It's a tricky topic to get your head round but I find it so interesting, it's just getting round the tricky bit of making sure everyone else can understand it - I know what I'm talking about so it makes sense to me.

If anyone is still unsure of finds it confusing let me know and I can try and reword things, or maybe throw in a few diagrams and so on.

[dannie_kl]

i dont have time to read it just now as have to go out but am going to print it off so i can read it at my leisure. also then i can re read it when something takes a bit to sink in.

[Tulip]

Just bumping this thread because of recent discussion of genetics - thought people might like a read!

[dannie_kl]

beth you dont need to bump it as its a sticky it stays at the top

[Tulip]

I know, but I never search through forums for new posts, just hit the 'Unread posts' button, so I'd have missed this otherwise! It's a grand thread though, even if it takes me a while to chew!

[debshar]

Hi I found this very interesting but totally confusing!! Asked my vet to explain the basics too. I have a year old salt & pepper bitch and am hoping to get a pure white male puppy soon. If I were to mate them in the future would the puppies probably all be salt & pepper? My mini has a black & silver father.

[zeta1454]

Hi I found this very interesting but totally confusing!! Asked my vet to explain the basics too. I have a year old salt & pepper bitch and am hoping to get a pure white male puppy soon. If I were to mate them in the future would the puppies probably all be salt & pepper? My mini has a black & silver father.

I don't know if this is a hypothetical question but if so I would say that you could not count on getting all salt & pepper from a mixed coat colour mating. As you have the black & silver gene on one side, if it is also in the other line too, there is always the possibility of black & silver pups. You can get black and silvers from 2 pepper & salt dogs mated if both lines carry the gene.

If you are seriously considering breeding do look at the discussions on the breeding threads on this Forum. It needs a great deal of thought as to why you would want to breed and a good knowledge of the pedigrees of the dogs you are using just to start with. You also need to be aware that most responsible breeders put an endorsement on their puppies' KC registration papers to indicate that they do not want the dog used in any future breeding and to prevent the KC registration of any puppies bred without their consent. This may apply to your current bitch or the white male you are looking to purchase.

[black beard]

The knowledge gained in colour genetics has recently been updated and you may find that the above post may be considered out of date in some areas.

Good post from Zeta

[Snazy]

breed white - p/s you will get p/s and maybe black

if both sides carry for b/s then you might get that

if both side carry for white, then you might get that

really depends on what you have in the pedigree and how it shows itself.

My friend recently did just that colour cross and got 2 white puppies, the p/s dam has a p/s parents but also a white grandsire.

[Tulip]

Hello Jo, how nice of you to pop up out of the BLUE!

[jaegervalder]

It's the same principal as the tall and short genes in humans....... I have 2 short ones! Although the father of my children is 6' 1' my youngest daughter is only 5' like me. But she may carry one of her fathers tall genes!