GENETICS OF THE BURMESE CATJOSEPH C. THOMPSON, VIRGINIA C. COBB, CLYDE E. KEELER*, ANDTH E first "Burmese" cat (see Figure 10) was a female imported into
the United States from Burma by
the senior author in the year 1930. Its
bodily confirmation and behavior weretypical for native Malay cat stocks, best
represented in America by the Siamese
variety. The Burmese was not recognized at once by the fanciers as a newbreed, but suffered for some time thecnus of being considered by most persons as an "off-colored Siamese." Thisexplanation sounded very plausible toowners of Siamese who knew that usually
the body color of the Siamese darkens"with age and varies to a certain extent
with the seasons of the year. To makematters worse, the first Burmese cat did
not breed true, but threw both Burmeseand Siamese kittens when mated to its
nearest available Malay cat type, theSiamese (see Figure 13D).
Two of the present authors (C. E. K.
and V. C.C.) at once recognized the first
Burmese cat as belonging to a new "incipient true-breeding variety." On thebasis of crosses made by the senior author, and through a paper (by C. E. K.
and V. C. C.) in 1934 one of us (V. C.
C.) proposed1 to the Cat Fanciers Association that the Burmese be recognized
as a new color variety for show purposes. Agitation was continued until its
acceptance in 1936. Burmese are now
eligible for registration in the Association Stud Book.
Further crosses by the senior author
produced the foundation pedigree of thebreed, shown in Figure 11. In this chart
it will be noted that, starting with theimported Burmese cat. Wong Mau, containing one gene for Burmese and one
gene for Siamese, and by mating this toa Siamese. Tai, it has been possible toestablish a Burmese variety that hasbred true for three generations.
The official standards 2 for Burmese
call for a Siamese conformation, a choco-late brown body color with seal points,
and topaz eyes. The kinky tail common
to so many Malay cats has not been bredout of Burmese stock and is generallypresent.
It was recognized that Mendelian segregation of two coat colors was taking
place in crosses of the imported Burmese
to a Siamese male, as will be seen inFigure 13/X The light colored kittens always developed into typical sealpoint
Siamese cats with china blue eyes, andthe dark kittens all became Burmese
cats with topaz colored eyes. There
were no intermediate color gradations
observed.
From crosses of this sort made by thesenior author there resulted 11 Burmese
males, 16 Burmese females, 11 Siamesemales and 10 Siamese females.
Mr. Mel Friedlander mated a Burmese female with a Siamese male. Thiscross produced four Siamese and fourBurmese.
One of us (V.C.C.) crossed a Burmese female to a Siamese male. Thereresulted three Siamese and two Burmese. In all, such crosses have produced
a total of 34 Burmese : 27 Siamese.
Because these four segregating classes
were present in relatively equal numbers, it was suspected that they represented a monofactorial toackcross involving one contrasted pair of autosomallyborne gene alleles, or that some independent autosomal gene manifest only inthe presence of the Siamese pattern, wasconverting certain genotypically Siamese
kittens into Burmese. •It soon became apparent that all genes
involved must be autosomal because of
the numerical equality of the sexes inboth Siamese and Burmese categories.
Thus, the possibility of the genetic complication of sex-linkage was readily dismissed.
It had been shown previously by twoof the authors (C.E.K. and V.C.C.) that"The Edgewood School, Greenwich, Connecticut.
119

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MADELEINE DMYTRYKThe Journal of Heredity

120

Figure 11

Squares represent males, and circles females.
The solid black symbols indicate pure breeding
Burmese. The half shaded symbols indicate
Burmese X Siamese hybrids which carry one
gene for Burmese and are intermediate in color. The unshaded symbols indicate the pureSiamese. The production of a pure breeding
Burmese breed was very easy because of theintermediate coloring of the Burmese X Siamese hybrids. (See Figure 12.)

If Burmese represents an intermediate allele between silver and Siamese,Daughter ot the first Burmese cat, Topaz we can make the following predictions:
Mau illustrates the type. Burmese is a dark
1. When Burmese is crossed to norvariant of the Siamese. It is an intermediateallelomorph of the albino series, between silver mal intensity (Figure 135) all of the offspring will exhibit normal intensity ofand Siamese.
pigmentation.
2. When pure bred Burmese is matthe gene producing "Silver" or "smoke" ed to Siamese, all the kittens should be<• Figure 13C) in cats is an allele or alter- Burmese.
native form of the same gene that pro3. All Siamese segregates from crossduces the Siamese coat pattern. Both es involving Burmese should breed true
silver and Siamese coats are affected by for Siamese.
"temperature and age, and both types have
4. When Burmese (whether purepoints darker than the body color. This bred, or hybrid for Siamese) is mated tois more evident in the non-agouti or non- silver or smoke, the offspring should alltabby form, namely, smoke.
be silver or smoke rather than tabby or
From the results of these experiments, black, as is the case when animals bearcoupled with the fact that the Burmese ing two Mendelian coat colors due toalso has dark points and that the body genes at independent loci are involved.
coat darkens with age, it appeared thatThe stud. Pak Kwai Mau (Siamese
Burmese might well represent a physio- segregate of the first Burmese, Wonglogical intermediate between silver and Mau by a Siamese sire, Tai Mau) hasSiamese. If a physiologically intermedi- sired more than 500 kittens of Siamese
ate stage between these two coat colors, queens. All of these kittens have been
it appeared probable that it might be an Siamese without a suggestion of Burmallele. The breeding experiments were ese. Nor have the authors ever heard
henceforth conducted to test this hy- of Siamese cats having Burmese ancespothesis.
try, throwing Burmese unless matedTOPAZ MAU, BURMESEI ,..,,r,- 10

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FOUNDATION STOCK OF THE BURMESE VARIETY OF CATS

Thompson et al: Burmese Cats

121

Figure 12

These three grades of pigmentation of the Siamese and Burmese coats are shown in the kittens.
Left to right: thoroughbred Siamese, hybrid Burmese X Siamese, and purebred Burmese. The
heterozygote carrying both the Burmese and Siamese alleles is intermediate in color.

with Burmese. These facts are in linewith prediction No. 3.
Burmese has been outcrossed to catsof normal coat color intensity. All thekittens so produced were of normal intensity. This confirms prediction No. 1.
It was learned that where there wasopportunity for the Burmese gene to enter a cross from both parents, theremight be in addition to Siamese kittens,
two shades of Burmese kittens (Figure12). The lighter of the two shades developed into the coat color of WongMau. The darker shade developed intoa darker body color.
It is well known that in rabbits, rats
and mice an animal showing a memberof the albino series of allelic coat colors

will be lighter when hybrid for a lower
allele than if purebred for the given firstallele. Aware that we were probably
dealing with alleles of the albino series in
the cat, we suspected that these two typesof Burmese represented animals purebred for the Burmese gene (darker) andhybrid for the Siamese gene (lighter),respectively. A cross of dark Burmese
to Siamese yielded only Burmese kittens, in keeping with prediction No. 2.
Where two Burmese, each hybrid forSiamese, were mated, the 3:1 ratio wasobserved. The verification matings by
one of us (M.D.) gave 20 Burmese : 5Siamese. When these 20 Burmese weredivided as to color phase there were
found 3 dark and 17 light. We actually

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COLOR VARIATION IN KITTENSThe Journal of Heredity

122Figure 13

At the present time four alleles of albinism are known. These are shown here. The lightest form is the Siamese (A). Next in intensity of pigmentation is the Burmese (D), the kittens
shown are segregating for Burmese and Siamese pigmentation. The smoke or silver pigmentation (C) is intermediate between Burmese and the full tabby or black pigmentation (B) shown
here in a Persian kitten. A color intermediate between Burmese and Siamese has also beenreported, and complete pink-eyed albinism would also be expected to be a member of this series.

expect twice as many light as dark fora Mendelian explanation.
Prediction No. 4 was the most difficult of all to test, because so many matings between Burmese and Smoke failed
to produce offspring, to such an extent
that it was suspected that some sort ofphysiological block prevented interfertility "between these two varieties. But
the persistence of one of us (M.D.)
eventually resulted in a fruitful mating.
A Smoke-Persian female (see Figure13C) was mated to a Burmese (hybridfor Siamese). Five kittens resulted, allsmokes. This confirmed our final prediction, No. 4.

Conclusion
Thus, we may conclude from the results of all our genetic tests that:

1. The Burmese is a distinct, newcoat-color variety of the domestic cat,•having a sound genetic basis, in thatdark Burmese will breed true.
2. The Burmese coat color is based
upon the possession of a pair of Burmese genes (dark color phase) or of asingle Burmese gene and its Siamesegene allele (light phase).
3. Burmese and Siamese genes are
sharply contrasted in their effects, there
being no intermediate grades of coat color observed, and Mendelian ratios being
found in both F 2 and backcross matings.
4. The Burmese gene represents afourth identified allele in the albino
series which, naming the genes in orderof diminishing pigmentation produced,
are as follows:
1—Normal intensity (Tabby or Black)

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Thompson et al: Burmese Cats
2—Silver (Smoke)
3—Burmese
4—Siamese

Postscript

mediate allele between the one producing an intensity similar to that of Burmese and the one producing Himalayan isknown in rabbits, and a similar gene4(extreme dilute of Detlefsen) is known
in mice. These facts seem to make oursuspicion of the Honolulu variation representing a fifth albino series allele incats seem even more plausible.
Literature Cited
1. Report of New York Cat Show, NewYork Times, Nov. 23, 1934.
2. Standards for Burmese privately printed
by Cat Fanciers Association.
3.

KEELER, CLYDE E., and VIRGINIA COBB.

/. Hered. 25:181-184. 1933.
4. DETLEFSON, J. A. Amcr. Nat. 55:469473.

ARE WAR MARRIAGES EUGENIC?
OME notes based on discussions with college students. The discussions were centered on the hasty marriages of young men
who are going away in the armed services.
A—It seems probable that from the eugenic
point of view the war marriages are far moresatisfactory than average marriages of young
people of the same ages. Whether they aresocially desirable is another matter to be considered later.
War marriages tend to tie eugenic because(1) The young men going into the armed
services are selected on the basis of physicaland mental tests. While these tests apply only
to the individual and do not consider genetics,
they certainly in the mass tend to select extra
good genetic probabilities. (2) The selected
men of the armed service tend to marry womenwhose physical and mental qualities appear tobe very good. We could be more certain on
this point if many thousand recent war brides
were given the physical and mental tests required of their husbands. Guessing is notscience, but it is a safe guess that the vast
majority of the war brides would pass thetests that selected their husbands for service.
In this connection it is interesting to mention
that there are some good reasons for expectingthat a smaller percentage of women than ofmen would have been rejected if the two sexes
had been called on the same basis to the selective examinations. (We must keep in mind
in these discussions that many defects which
affect health and efficiency in the armed services have nothing to do with heredity andeugenics.)
Summary: From the eugenic point of view
war marriages look promising. They are as
eugenically good as we could make them if theSarmy medical and mental tests were required
for all marriage licenses. We could do better
only by requiring genetic examinations forlicenses. After the war we are going to bemuch more interested in physical and mental
examinations as a basis for proposed healthimprovement campaigns. Perhaps indirectly
this will encourage interest in the eugenic
movement.
B—The students in these discussions weremore interested in the social aspects of war
marriages. It was agreed that from the social
point of view the hastily planned marriages(not the long engagements) were problems.
That proved so in many such marriages in
1917-19. Hasty war marriages are probably
greater risks than hasty marriages in normal
times. The reason may be that in wartime thewedding is commonly followed by long separation without the opportunity for post-nuptial
adjustments that so often make hasty marriages successful when the newly-weds live
and work and play together after the wedding.
Summary: In the cases of preceding closeacquaintance, especially engagements, immediate marriages when the men were leaving
for war in 1917-19 were commonly sociallysuccessful. Hasty marriages based on shortacquaintance and wartime emotions were sooften social failures that they should not berecommended under present conditions. Most
participants in the discussions were inclined toadmit that it is now impossible to plan postwar economic matters affectine families fromwar marriages or any others. Hence economic
arguments have little weight with the young
folks concerned.
M. A. BICELOW.

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A color variation darker than ordinary
Siamese was discovered by Lelia Volkof Honolulu to be segregating in her
Siamese strain. This was examined by
one of us (C.E.K.) and found to be intermediate in color between Burmeseand Siamese, and hence we suspect theHawaiian variation to represent a fifthallele in the albino series. It is so near
Siamese in color, however, that it willprobably not 'be perpetuated as a distinct
variety and hence the possibility willprobably not be had of checking its
genetic relationships. At least one inter-123