Sunday, April 4, 2010

Spoonerisms: Siamese Tails

Dipity Discovers Spoon's Chair While I knew Siamese cats get their coloration pattern from a mutation of melanin (actually, as I found out, it's tyrosinase, an enzyme involved in melanin production), I decided to do some more digging to find out about lynx-points like my Dipity. The short-lived biology major in me got excited about some of the things I found.

Basically, Siamese have partial albinism because of an ancestral recessive mutation in tyrosinase. The enzyme breaks down at higher body temperature, so areas like the belly don't produce melanin while cooler areas (the "points") do. A seal-point (the darkest coloring) is just a solid black cat, as far as the color genes are concerned. The black is incompletely expressed because of the broken pigmentation production. Furthermore, all Siamese have the partial-albino blue eyes because of the same mutation. Judging from the other oriental breeds which probably have a common ancestor, pure Siamese probably have genes for green eyes.

Now to the lynx-point. Tabbies aren't a breed, per se, although what constitutes a breed can be rather arbitrary. Their markings come from the combination of two genes. The first is an autosomal-dominant gene which alternates pigment production at various points of a hair's growth, resulting in the striped single hairs Dipity sheds on me. Solid-colored cats actually arose from a recessive mutation in the ticking gene. After all, domestic cats descend from striped and spotted wild cats. The tabby gene mixes these ticked hairs with solid hairs in the classic tabby patterns. These genes were bred into the Siamese line to produce lynx-points. Lynx-points would have to be at least 3/4 Siamese by breeding if bred from pure Siamese, though, since the Siamese melanin-deficiency comes from a recessive gene.

So that explains a lot. Dipity definitely has the partial albinism of a Siamese. She also has the voice and even slightly-crossed eyes. She, uh, seems to lack the typical Siamese intelligence, though, although she does have the sociable disposition. She's already occasionally attempting to be a lap cat, which usually starts in older cats in my experience. I'm not sure if her tendency to get into everything is due to Siamese curiosity as much as her youth. Her head isn't really either of the standard Siamese shapes (the "traditional" apple or the "modern" pointy triangle), though, more like a slightly flattened apple. But she's still super-cute!

No comments: