Member of the Internet Link Exchange

THE WHITE SPOTTING GENE IN THE RAGDOLL

Dr David Richardson M.B..B.S. (Hons)

Jacqui Richardson

RAGAJAC RAGDOLL CATTERY

INTRODUCTION

The white spotting gene is a highly variable, hard to control gene which produces white spot, randomly or patterned over they underlying coat colour. It is my belief that the white spotting gene is most probably actually a series of genes close together on a single chromosome, known as a polygene. This is what makes it so variable.

In Ragdolls the action of the white spotting gene on the Himalayan patterned cats (i.e. Points) causes mitts through to bicolours through to high whites.

THEORIES

In the literature there are two different explanations of the white spotting gene:

The first theory ^1,2 is that the gene has:

A dominant form - S - which produces white spots on whatever the underlying coat colour is; e.g. White spots on a black house cat.

A recessive form - s - which is less likely to be expressed.

This theory has the homozygous gene SS producing the most or largest areas of white, causing (I know this is a "no, no" in articles about Ragdoll cats, but I am going to use the terms anyway) harlequins, vans and high white coat styles.

The heterozygous form - Ss - produces smaller amounts of white e.g. Bicolours and smallest of all, the mitted.

The recessive form - ss - i.e. double recessive is what our himmy pattern ( blue,seal, choc or lilac) cats are with no expression of the white spotting gene at all.

 

In my opinion the problem with this theory is that it allows for no explanation for regular placement of the white spots e.g. In the bicolour with its "V" on the forehead or the mitt with it’s regularly placed spots on all four feet.

For this reason I prefer the second theory ³ which:

Incorporates the first theory but with two additional components which if present help regulate the placement of the white spots. These alleles i.e. subgroups of the white spotting gene, are :

Sp -( p - is for particolour) which causes in its pure form the bicolour pattern with white belly, legs, feet, chin and chest plus the "V" on the forehead.

Sb - (b - is for birman) which I believe causes both the mitt pattern in Ragdolls and the glove pattern in Birmans.

Sb and Sp are not mutually exclusive, and may both be absent or swamped by White Spots in the S,S high white cats.

If a Ragdoll carries both Sp and Sb it probably will look more bi than mitt, or it may appear as the so called mitt-bi. I must confess that we have a very attractive mitt bi here at presnt, with quite good bicolour pattering except for a large mitt on one front leg.

I feel that as we get bigger amounts of the white spotting gene eg Ss or SS forms, the Sp and Sb alleles become swamped by white patches and so cease to be apparent, giving a van or harlequin pattern.

I believe all Ragdolls carrying the white spotting gene carry either the Sp and/or the Sb allele. If both were absent we would see many more ragdolls with a truly random white spotting pattern similar to that seen in many housecats.

 

Birmans all carry the Sb allele of the white spotting gene which is why they are all gloved. No Birmans carry the Sp form or there would be bicolour patterned Birman’s.

CURRENT CONTROVERSIES

There has been some recent debate over whether the:

* Birman gloving allele is different to the mitting allele in the Ragdolls. ⁴

My feeling is that it must be the same allele because it would be almost ridiculously coincidental for two such similar cat breeds to have two entirely different alleles both causing white feet.

The big difference between the Sb in Ragdolls and the Sb in Birmans would seem to be that if you put together two Birmans you get consistently gloved cats while if you put together two mitted Ragdolls you may get mitts or a bi patterned cat or even a point. However further breeding of these Bi Ragdolls seems to revert to the mitt pattern indicating that they are not true Sp allele bicolours.

These differences may be as a result of the very tight breeding for gloved patterns over the last thirty years in Birmans ⁵ and a more open breeding style in the Ragdoll leading to less consistent subgroups of the Sb allele finding expression in our Raggies.

I feel the subtle differences between the gloves in Birmans and the Mitts in Ragdolls are simply due to ongoing refinement breeding over many generations in both breeds.

The other area for debate is whether:

* the mitt "gene"( - in my opinion actually an allele or subgoup of the white sptting gene) is dominant over the himmy pattern, with some prominant geneticists ⁴ saying that it is. In my opinion there is no complete dominance either way, probably because of the polygenal nature of the white spotting gene.

In a recent Internet survey by the authors ⁹, we obtained a large series of results of offspring from pointxmitt ragdoll matings. The results are summarised below:

In our series of Ragdoll point x mitt matings, we obtained stats on 443 kittens from 17 catteries.

They seem to separate out into two groups, 17.5% of the cats in populations of kittens where there is close to a 1:1 point:mitt ratio, and 82.5% of kittens being in a group where an approximate 3:2 point to mitt ratio predominates.

The first group is explainable if the mitt gene IS dominant over the point ie ss(point) x sSb gives:

ie giving a 1:1 point:mitt ratio.

The second group with the 3:2 point to mitt ratio is explained by Lorraine Shelton ¹⁰ as being due to the incomplete dominance of the mitt over the point, the 40% mitt being called the penetrance of the gene in this situation.

Randomness Increases with Degree of White Spotting Gene

Another interesting feature of this amazing gene is that variability of appearance of the cat increases with increasing levels of the gene.

For example using the terminology for wsg in ragdolls: Sm is mitt allele, Sp is bicolour allele :-

ss = point no wsg - this has 100% reliability

sSm = mitt in my survey of 443 kittens this had 97.6% reliability

SmSm = bicolour this seems to have less reliability (untested)

sSp = bicolour less reliability of colour placement still ie many mismarked

SmSp = bi mitt even more variable can look bi or mitt bi or?

SpSp = van becoming high white, less reliability still.


So from the top of this table to the bottom you have increasing unpredictability of outcome for breeders. It may even be feasible to work out the level of predictability of the placement and amount of the white spots (by doing more breeder surveys for example)and then change the order of the table.

IF this is true one could postulate a LAW THAT AS THE LEVELS OF WSG INCREASE SO DOES THE UNPREDICTABILITY OF OUTCOME.

GUIDELINES FOR BREEDING WITH THE WHITE SPOTTING GENE

• Avoid homozygous white spotting gene mated with white spotting gene as this will produce increasingly high white cats.
• Some ⁶ say it may be useful to have a relatively high white Ragdoll (van or harlequin pattern style) to breed with points with the aim of getting well marked bicolours. However others ⁷ say that most bi’s achieved by this method are usually mismarked.
• It may be that the best looking "bicolours" for the show bench or the pet market can be most consistently achieved by mating selected mitts to selected mitts. ⁸ However these are not true bicolours as they do not carry the Sp allele of the white spotting gene and further mating with these cats will rarely produce more good bicolours.
• The best way of producing bicolours for breeding is probably to mate selected mitts to selected Bicolours and then mate points with the prodigy because this is getting the best of all worlds ie. The Sb allele from the mitt, Sp from the Bi and avoiding too much white developing by breeding back to the point.
• When mating points to mitts you can expect roughly 60% points to 40% mitts in most cases.

 

CONCLUSION

The white spotting gene allows us to have mitts and bicolours in our Ragdolls. It is a highly variable gene due to polygenes. More homozygous forms produce more white in the coat. The Sp and/or Sb alleles (i.e. subgroups) of the white spotting gene are present in all Ragdolls with the white spotting gene and bring about some degree of control of the placement of the white and therefore better choice as to the coat patterns of our cats.

REFERENCES

1. Marie Rihova- 88 Hints for Cat Lovers. Pub. Sunburst Books.
2. http://www.kkoe.co.at/kkoe/genetic/gcolorw.htm
3. Nancy Creek and Roger Breton. http://www.best.com/~sirlou/catgenetics.html
4. Lesley A Lyons, PhD. The Australian/International Ragdoll Advisory Club Newsletter. Vol.5 Dec. 1996.
5. Lorraine Shelton. The Australian/International Ragdoll Advisory Club Newsletter. Vol 5 Dec 1996.
6. Cathy Walker. Gradach Ragdolls and Maine Coons, in discussion.
7. Tracy Alsop. Dollywood Ragdoll Cattery, in discussion.
8. Angela Irvine. Ragtails Ragdoll Cattery, RAS cat control Ragdoll seminar, Sydney April 1997.
9. RAGS Internet list survey Jacqui and David Richardson , June 1997.
10. Lorraine Shelton in email to TICA.forum list June 1997.

 

Home|Thumbnail Gallery|PictureGallery 1,2,3,4,5|Feline Genetics|Ragajac Kitten Info|Links| Email us|C.O.O.L|Jacarouge Red Ragdoll Program|