from gloria stephens

Ian A. Boussy iboussy at orion.it.luc.edu
Thu Jul 20 16:08:34 EST 1995

Actually, the Siamese pattern is best thought of as a temperature-sensitive albinism that can 
partially mask any background color.  When it masks orange tabby, one gets orange tabby "points"; 
when it masks black, one gets dark points ("sealpoint siamese").  The siamese pattern itself is 
recessive; the normal allele at the siamese locus permits expression of any color at any 
temperature (i.e., anywhere on the body).

The cross between a sealpoint siamese and a tabby yields offspring that are heterozygous at the 
siamese locus, and thus the dominant normal allele allows expression of other color genes.  Since 
the black background color of the sealpoint siamese is dominant over many other colors (e.g., 
whatever the tabby offered), black kittens are often the result.

Following on, in the second generation of sibmating, the siamese pattern should again manifest 
itself among 1/4 of the offspring, superimposed on whatever colors they inherited.

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