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.
