Question about colour genes

[Dawn F]

thanks Witty, I'll try and track it down

[Reynard]

Dawn, I guess I had my interest piqued by various friends I've gotten to know in the cat fancy. 

Ah yes, "Genetics for Cat breeders" by Robinson, I'd imagine. I have a copy - it's quite a toothsome tome, but I've found it no worse than any engineering text I've had to wade my way through... 

The Book of the Cat is probably a far better introduction to cat genetics - it's out of print, but can still be found.

[Dawn F]

I do find this really interesting - you've obviously got it sussed Witty!!  I got a secondhand book from amazon called genetics for cat breeders or something but I can't follow it at all!

[Reynard]

No worries Julie! 

Actually, your boy looks like a ginger - the stripes on him are actually quite rufous although the coat ground is a little on the pale side but nothing overly unusual. If anything, Desley's cat is a cream and white. A good tip to tell the difference is that a cream cat should be sort of the colour of a rich tea biscuit. 

Bearing in mind that this website is American, it's actually a brilliant guide to coat colours and patterns: http://www.seregiontica.org/Colors/intro.htm

Hope this helps. 

[Desley (booktigger)]

I wouldnt say his face is paler than a true ginger to be honest Julie, and dont forget gingers come in different shades - we currently have a dark ginger tabby, and I know they are rarely that dark, and we have an incredibly pale ginger, never seen one of his colouring before - mind you, one was bought as a Bengal cross, and one has Bengal cross on vacc card.

just to compare here they are

[Canterbury_cats (Sharon)]

Fab names,,,,, so all now is a photo of Toast (who i presume is female)!

[Pinkbear (Julie)]

Haven't got a clue what to call them.  What about Marmite and Toast? 

[Canterbury_cats (Sharon)]

Hi Julie

Do we have names for these last two kittens Julie..  ? I will nick that photo for the website?

[Pinkbear (Julie)]

Managed to get a pic of the little tyke! 

The photo has come up darker than he actually is - not a good camera - but you can see his face is paler than a true ginger. 

[Pinkbear (Julie)]

Cheers, Reynard, you're a star! 

I think when this little chap is ready, he may attract a bit of extra attention if we list him as a cream kitten. 

[Reynard]

As ever I see I got my terms wrong in discussing these things. When I described the tortie as diffused I meant dilute - the colours are patched but bleached looking.  She is the only one there with this variation so I wondered if this was a gene type that could have been dorment or just a random mutation.

Julie, random mutations are extremely rare and what most folks call a "dormant" gene is just a simple recessive gene.

The gene for dilute (as opposed to full colour expression) is a recessive gene that acts to reduce the pigment concentration in the hair shaft, turning red to cream and black to blue (grey).

For a cat to have a dilute coat, it needs two copies of the gene d i.e. it must have a genotype of dd, one from each parent. From what you describe, apart from this blue tortie and white queen (and possibly her son), you don't have any other dilute cats in the colony - this implies that her mother and the tom she mated with are carriers of dilute but not dilute themselves, having a genotype Dd and showing full colour expression.

This means that when two Dd cats mate, there will be a ratio of 3 full colour expression kittens to one dilute kitten - although this is not always the case given the randomness of egg fertilization.

As for this queen's son, he could therefore actually be a cream as opposed to a ginger as his mother is dilute and there is a pretty good possibility of one of the toms in this colony also carrying one copy of the dilute gene.

It's a bit like Pearl really - she is a blue, but in the colony where she lived, all the other cats (and her two litters of kittens) were black. You can't tell whether a full-colour cat carries the gene for dilute until it throws up a dilute kitten.

I guess you can tell I'm fascinated by cat genetics... 

As for the black coats, it's mainly the damp that makes them go rusty, though the sun has something to do with it too - it was significantly wetter last year than this. This has nothing to do with genetics - just ask those folks in the cat fancy who show black cats... 

[Pinkbear (Julie)]

You see, I knew you guys would blind me with science and I'm not much wiser... 

Actually, yes it does explain a few things I've seen so thanks!  You got it dead right, Reynard - last year the torties had ginger and tortie females and black and ginger males. I knew that old ginger tom was responsible for a lot of it and was dead glad to remove him from the pool! 

I accept what you say about the 'rusty' look to the black ones as you've studied this and I haven't, but last year all of the kittens did seem to have distinct orange tinges behind their ears and this year they don't. So much so that I swear I could tell which kittens had come from this site and which didn't. Maybe it was just sunnier last year, then? Maybe I was just looking for evidence of inbreeding and thought I'd found it? Who knows! 

As ever I see I got my terms wrong in discussing these things. When I described the tortie as diffused I meant dilute - the colours are patched but bleached looking.  She is the only one there with this variation so I wondered if this was a gene type that could have been dorment or just a random mutation.

Anyway all good stuff and very interesting to know, guys, thanks! 

[Reynard]

Sharon, no matter who the father or fathers were, this kitten's father has got to be black. That's all that's left up there now in the way of toms. And mum was definitely a diffused tortie. 

Reynard is good at this stuff! Where are you? 

Not necessarily, see post below...  The ratio of colours for a tortie-ginger mating will be 1 tortie, 2 ginger and 1 black. However, despite that being the ratio, there's still no guarantee you'll get any of these as it is truly random in real life.

I was in the middle of posting.   

When you say diffused, do you mean a brindle tortie or a dilute?

[Reynard]

Julie, I think your black tom with a ginger undercoat is just an ordinary black tom - black cats will go "rusty" if they have outside access - my Toby looks almost ch0colatey at the moment. This is due to the effect of sun and moisture on the coat. Ever wonder why black show cats are so black? It's because they are kept indoors...   Also, black kittens tend towards the "rusty" anyway, the colour will fade when they grow in their adult coat.

The variation of the colour in the red (ginger) gene is down to what are known as polygenes. These act on the strength of the colour and while it's not exactly understood how the polygenes operate, the high intensity of the show cat red (ginger) is achieved through careful selection during breeding. Obviously, with mogs, or in this case ferals, this selection is far more random. So some mog ginger cats can be so pale as to be almost cream i.e. theit genotype is red, but the phenotype is cream i.e. the dilute of red.

Unless that is, you have males and females carrying the dilute gene, which would give you creams, blues and blue-creams.

The black gene is not dominant - it is a recessive of tabby, where the agouti (banding on the hair) is turned off. But a black cat must have two copies of the non-agouti gene, those cats with only one copy will still be tabby.

As for the red gene, that's trully an odd one as it's sex-linked. The red gene, O, is only carried on the x-chromosome (there is no space for it on the y) so a male ginger cat only has one copy of the orange gene and can therefore only pass it onto his female offspring. On the otherhand, a female cat can have two different manifestations; it can have one copy of the gene (Oo) in which case the cat is tortie or it can have two copies of O in which case she is ginger. The patching of the tortie on a cat is random btw.

Now you say you had a ginger tom lurking last year? If he mated with the tortie females, you would have had ginger and tortie females and ginger and black males. The black males will have NO copy of the red gene, therefore it stands to reason that this will not affect coat colour.  

[Canterbury_cats (Sharon)]

Does this help!! its all to do with female!! Due to the x chromosome!


The sex-linked orange gene, O, determines if there will be orange fur. This gene is located on the X chromosome. In cats with orange fur, phaeomelanin (orange pigment) completely replaces eumelanin (black or brown pigment).
Males have only one X chromosome, so only have one allele of this gene. O results in orange fur, and o results in non-orange fur.
Since females have two X chromosomes, they have two alleles of this gene. OO results in orange fur, oo results in non-orange fur, and Oo results in a tortoiseshell cat, in which some parts of the fur are orange and others areas non-orange. A cat with Oo and white spotting genes is commonly called a calico. The reason for the patchwork effect in female cats heterozygous for the O gene (Oo) is X-inactivation - one or the other X chromosome in every cell in the embryo is randomly inactivated (see Barr body), and the gene in the other X chromosome is expressed.
Rufous polygenes, as yet unidentified, can affect the richness of the orange gene's expression.
For a cat to be tortoiseshell, calico, or one of the variants such as blue-cream or chocolate tortoiseshell, the cat must simultaneously express two alleles, O and o, which are located on the X chromosome. Males normally cannot do this, as they have only one X chromosome, and therefore only one allele, and so calico cats are normally only female. Male tortoiseshell or calico cats occur only if they have chromosomal abnormalities such as the genotype XXY (in which case they are sterile), chromosomal mosaicism (only portions of their cells have the genotype XXY, so these cats may be fertile), or chimericism (a single individual formed from two fused embryos, at least one of which was male). Approximately 1 in 1000 calico/tortoiseshell cats are male. Chimericism (which may result in fertile male cats) appears to be the most common mechanism.

[Pinkbear (Julie)]

Sharon, no matter who the father or fathers were, this kitten's father has got to be black. That's all that's left up there now in the way of toms. And mum was definitely a diffused tortie. 

We did have 3 ginger females from this group last year, remember? All from the same litter. We were all very surprised at that one! 

Reynard is good at this stuff! Where are you? 

I was just curious, that's all. Never had a chance to study these things before but it's facinating trying to figure what happened. 

[Canterbury_cats (Sharon)]

I think i am right in saying that when queens are mated the kittens may be from different fathers!

I actually thought ginger was the dominate colour then the black.. Is would also depend on the sex of the kittens etc and usually gingers are male (although you can of course get females) female being less common. Doing genetics at University i should be able to work this out, but we need to have a clue as to the mum and the dad to work out the resulting kittens and different proportions of each. Certaintly torties would less domiante than the ginger i think.. Anyhows very interesting!

[Pinkbear (Julie)]

I know we often discuss colour genes but I don't think this particular question has been covered... 

I've been working to TNR a colony for a year now. It's hard because it's mostly open fields and woodland and although I've done 40+ of them so far, a few still aviod me and we've had some more kittens this year.  I'd say a good 95% are black (although quiet a few have a few white chest hairs). Around 3-4% are black and white.

We also have 3 tortie queens, one of which was a patch tortie spayed last year. One is mostly black but with flecks of ginger - very pretty! The remaining tortie is the daughter of the patch one but is diffused. All these torties, both last year and this year, have produced kittens that were either ginger, ginger and white, black and white or pure black.

My question concerns one of this year's kittens I caught yesterday. He is a male ginger and the son of the diffused patch tortie. His coat isn't diffused but it's not really a strong colour either. It's sort of inbetween. Thing is, although we did have a ginger tom last year (whose presence was obvious because all the black kittens last year had a ginger undercoat  ) I TNRd him last autumn and the only full Toms left are pure black. I would show you a picture of this kitten but he's quite unimpressed with my hospitality so far and refused to pose for my camera. 

So... how do diffused genes occur? It is a one off mutation or does it lay dorment? If it lays dorment, isn't the black gene stronger and would cancel it out? Is there such a thing as half-diffused? 

Ove the the floor...