Copyright 2010 Sarah Hartwell

This page pulls together what is known about Don Shaw's Barrington Brown gene, a form of recessive brown/colour dilution only reliably recorded in a colony of laboratory cats, none of which are believed to have left the laboratory. To make this comprehensible to the non-genetics expert I have referred to "copies of genes" or "versions" of genes although the correct terminology is "alleles". There is also a brief guide to Shaw's terminology at the end as Shaw's writing pre-dated modern "standard" symbols and terminology.

Don Shaw was an early feline geneticist in the USA. During the 1950s and 1960s, there was no standard form of genetic coding and Shaw used his own system of genetic coding which can be difficult to read today. He also referred to chocolate, which is a mutation of the black gene, as "chocolate dilution". What modern fanciers call dilution, Shaw called "maltesing" (Maltese i.e. blue cats were a genuine dilution of black). Shaw viewed dilution as being due to the reducing amount of melanin present in the hair and not by the way pigment forms clumps in the hair. Chocolate had less melanin than black, therefore Shaw called this dilution. Blue has a the same amount of melanin, but arranged differently, so Shaw did not consider this dilution.

In simple terms, the black (eumelanin) colours in cats is due to a series of genes (alleles to be precise) with the following order of dominance/recessive (most dominant at the top, most recessive at the bottom). The chart also shows how these combine with dilution genes and dilution modifier genes. A cat inherits 2 copies of the black gene and only the more dominant version will show up while the recessive gene will be hidden. The caramel form only shows up in cats that already have the dilute colour and it lightens and adds a brownish cast to the dilute colour.






Caramel (UK: Blue-based caramel)


Lavender (Lilac)

Taupe (UK: Lilac-based caramel)



UK: Fawn-based Caramel

These colours will naturally look a little different on Burmese (due to the sepia gene), Tonkinese (mink gene) and cats with the silver Inhibitor gene. For clarity, this article will ignore those additional genes and just look at the eumelanin (black) series of colours.

An additional type of recessively carried brown colour has been reported in laboratory cats, but not in the outside world. Termed "Barrington Brown", a cat with two copies of this gene had black pigment diluted as shown below. Because it hasn't (yet) been seen in the cat fancy, this gene is enigmatic to many fanciers. Some have suggested it is the same as caramel (dilute modifier), however some reports indicate cats with 2 copies of the Barrington Brown gene were different in colour from cats with only one copy of the gene (which seems odd since the gene is recessive and cats with only one copy should have dilution at all). When 2 copies were present, Barrington Brown had an additive effect on black and chocolate, and presumably on cinnamon (which may have been unfamiliar to Shaw).




Deep mahogany brown


Light brown


Cafe-au-lait (milk coffee colour)

The dilution only happens if 2 copies of Barrington Brown are present, although some sources suggest the genes had additive effect on each other to create the pale milk coffee coloured cats when there were 2 Barrington Brown genes. Since Barrington Brown is a recessive gene. If only one copy was present it should be masked by the dominant non-Barrington copy. This is part of the problem when interpreting reports that use an old, non-standard genetics notation!

ba - Barrington Brown Locus (unverified)





Homozygous - Non Barrington Brown

Cat unaffected - i.e. Black/Brown/Chocolate etc


Heterozygous - Non Barrington Brown - carrying Barrington Brown

Cat unaffected - i.e. Black/Brown/Chocolate etc


Homozygous - Barrington Brown -liberty of renaming

Mahogany Brown/Light Brown/milk coffee in colour (depending on whether cat is black/chocolate/cinnamon)

In the 1960s, chocolate was described as a dilution of black and the third possible version of the gene, cinnamon, was apparently unfamiliar to Shaw (or not reflected in his terminology). Shaw’s Barrington Brown article was first written in the 1960’s in the Journal of Cat Genetics, and reprinted in the early 1970’s in Cats Magazine and has been subject to much reinterpretation, especially when a dilute modifier emerged in the cat fancy.

According to Shaw's breeding data, Barrington Brown (mahogany brown) dilution was inherited in much the same way as “standard chocolate dilution" (black/chocolate alleles) by reducing the amount of pigment in the hair and by producing elliptical pigment granules instead of round granules. Elliptical pigment granules refract light differently and give a reddish-brown colour instead of black/sepia. In Shaw's terminology which can confuse modern readers, chocolate is a dilute of black (while blue is "maltesing" of black). It became apparent that Barrington dilution gene was in a different location to the ordinary black/chocolate genes and was inherited independently of black/chocolate. That means it wasn't the modern cinnamon. Genes in different locations can affect different enzymes involved in production of the same protein, in this case the production of eumelanin pigment. Shaw referred to the “standard chocolate dilution" as affecting enzyme D while the Barrington system affected enzyme B. He identified Barrington Brown as having 2 alleles; the dominant wild type and the recessive Barrington Brown dilution.

B+ = Wild type gene. Apparently responsible for normal Enzyme B production, giving full intensity of melanin.
b = Barrington Brown recessive gene. When 2 copies are present there is less Enzyme B produced which means less melanin produced; the pigment granules are elliptical (reddish-brown) instead of round (black).

He gave it the name Barrington Dilution or Barrington Brown because it was discovered at the Quaker Oats Nutritional Laboratories in Barrington, Illinois. The first cat known to be homozygous for Barrington Brown was born at the Barrington Laboratories. This was a strangely colored light brown (rich caramel or perhaps cafe-au-lait) male kitten homozygous for Barrington Brown as well as having “standard chocolate dilution". The 2 gene systems were additive in nature and each expresses its effect as if the other were not present i.e. the end result is the sum of both Barrington Brown and "standard chocolate dilution" being expressed. Shaw's description of "rich caramel" (light tan) misled 1970s breeders to believe the emerging dilute modifier was the same as Barrington Brown.

Don Shaw and Wayne Durdle investigated this gene in depth. Cats carrying the Barrington gene were donated by the Quaker Oats Nutritional Laboratory to the Feline Research Laboratory at Tuskegee Institute, Alabama (maintained there from summer 1966 to mid-1969). No Barrington Brown carriers were believed to exist outside of the colonies and Barrington and Tuskegee. Studies established that the light tan or cafe-au-lait colouration was due to the combined effects of "standard chocolate dilution" and their Barrington Brown gene. Shaw had left the project in July 1968 and Durdle reportedly terminated the colony in June 1969 (this suggests the cats were destroyed, neutered or used in other research). To their knowledge - and to the ongoing chagrin of many breeders - the Barrington Brown cats had no direct descendents in the cat fancy and the gene was lost. However, Shaw noted that some "doubly diluted" kittens were appearing in the cat fancy. These had no apparent connection to the Barrington or Tuskegee cats. He also mentioned unconfirmed reports of a dilution system similar to the “standard chocolate dilution" but not traceable to any known chocolate ancestry.

In Cats Magazine, April 1972, Gudrun Meier-Hedde wrote to Shaw "It would be an unforgivable sin if you let these alleles pass back into oblivion. I hope, you can help me find a cat for both of these alleles. I intend to do various breedings with them." Shaw replied "As for the Barrington allele, as was stated in the article, they were produced at the Quaker Oaks’ Nutritional Laboratories in Barrington, Illinois. There was another writer who did write me after the article and related that cats with the Barrington allele had been obtained by others including the original male '.$ 00' himself. I have no additional information as to the status of these cats. The Barringtons we had at Tuskegee Institute were obtained with the understanding that, they were not to be exploited in the cat fancy."

Shaw offered the following possibilities:

To identify the relationship, if any between the Barrington Brown cats and those with "double dilution" would require test-matings between the new "doubly diluted" cats and some known Barrington Brown cats. Since there were no known Barrington Brown cats outside of the laboratory and the lab colony had been terminated, this wasn't possible. In the 1970s, Pat Turner stated, without any supporting evidence, that caramel (the double dilution mentioned by Shaw) was the same as Barrington Brown. The dilute modifier (caramel) colours are not the same as the colours described by Shaw, though some websites continue to repeat Turner's claim that Shaw called the caramel colour Barrington Brown. Turner had simply jumped to conclusions. Barrington Brown cannot be the same as caramel because Barrington Brown affected black and chocolate, but caramel only affects blue, lilac and cream.

Shaw noted that recessive traits emerge in pedigree cats because of line-breeding and inbreeding which matches together genetically similar individuals. This means a better chance of cats inheriting 2 recessive versions of a gene and new traits showing up as result - just as they did in the Barrington colony of cats.

From a breeder viewpoint, it is sad that "recessive brown" has been lost. Shaw's descriptions indicate that it wasn't the same as caramel. Its effects on the wider palette of feline colours - torties, ticked and patterned tabbies, Burmese sepias, minks and colourpoints - can only be hypothesised. From time to time there are reports of odd colours in cats, including a tantalising "palomino" described as "the colour of a brown paper grocery bag" from the USA that might just have been the light tan noted by Shaw.


Modern feline geneticists use b/b for chocolate, but Shaw defined chocolate as d/d, because to him it was a dilution of black. Reading Shaw's work on black, chocolate and Barrington Brown without knowing his terminology is therefore confusing. In Shaw's defence, the standard gene symbols had not been defined in the 1950s and 1960s.

Light tan/cafe-au-lait in Shaw's terminology is d/d, b/b. To a modern reader, d/d, b/b indicates lilac. This, as much as any visual similarity, helps explain why his Barrington Brown is so often confused with the dilute modifier.

Shaw’s Chocolate alleles

D+- = Normal colour (black/sepia)
d/d = chocolate (in Shaw’ s words, Chocolate Dilution)

Shaw’s Maltese alleles

M+ = Dense colours e.g. black
m/m = Maltese (or in our terms dilution) e.g. blue is the maltese of black

Shaw's Barrington Brown allele

B+ = Normal coat
b/b = Barrington Brown

Lilac (in Shaw's terminology) would be d/d, m/m = Dilution allele (chocolate) + Maltese allele = lilac.
Lilac in modern terminology is b/b, d/d = Chocolate allele + dilution allele = lilac.

Although there is no official modern symbol for the lost Barrington Brown, Ba is often used for convenience in modern discussion (since it isn't allocated to anything else).

Brown Locus (modern symbols)

B/- = Black/Brown (Shaw's black/sepia)
b/b = chocolate (Shaw's "standard chocolate dilution")
bI/bl = cinnamon (probably not recognised by Shaw)

Barrington Brown Locus (modern symbols)

Ba/Ba - no Barrington Brown dilution
ba/ba - Barrington Brown dilution/recessive brown