It’s hard to provide the regular geek fare when kittens are involved, but I’ll try.
All of these kittens have the same parents, and both are the Ragdoll breed. Notice that the kittens are all white, but mama has dark fur at the outer body points. Over time the kittens will look like mama. Why?
The cats have a recessive mutation that results in a temperature-dependent albinism, where the triggering temperature happens to be very close to body temperature. In other words, the cat lacks pigment like an albino when at body temperature, but the pigment is produced when the cells are slightly below body temperature. This is why the kittens are all white when they grow their first fur in utero, and then the new hair that slowly grows out is dark only at the cooler extremities (ears, tail, snout, and paws). Scientists have been able to test this mechanism by watching a shaved cat regrow all white fur in a body-temperature-controlled room, or dark fur with selective cooling.
The kittens opened their eyes this week, and like mom, they are all blue. When cats, or humans, lack pigment in their eyes, the eyes are blue. The blue color is itself not a pigment, but a structural color that comes from the scattering of light off of the iris (the Tyndall effect). These cat eyes are close enough to body temperature to express the albinism trait.
In other words, we are all blue eyed, but most of us have brown pigment that hides the underlying blue. I saw a dramatic demonstration of this by a startup that has developed a laser treatment that can zap the brown pigment, and in their animal studies, turn a brown eye blue. In green eyes like mine, the brown pigment has a different mutation, shifting it to yellow and tinting my blue eyes green.
The back of the albino eye also lacks pigment, giving these cats’ pupils a retinal red reflection in the dark, unlike a normally pigmented cat’s green to blue eye-shine.
Recessive mutations like this point coloration in cats might be rarely seen if not for active human selection for what breeders see as cute. My parents’ cat, with the folded ears is another example.
Another detail that my kids noticed: when they are not in one big pile, huddling for warmth (like cellular automata), they tend to cluster in two piles of three, long before their eyes were open. And the two clumps would always segregate by nose color – three pink noses and three grey noses together. Here’s a random guess as to why. Mom has a grey nose; the rental husband was pink. Perhaps that expression of genes from Dad for one and Mom for the other is detectable by smell, and perhaps they have a homophily bias. It’s not implausible; a dog can identify whether pairs of humans are identical twins or not by scent alone. (more on this in my puppy post on flickr)
When they all look the same, naming them early might be tough. My daughter wants to name one “static” and my son immediately suggests “public static void main” =)
P.S. mutation details footnote: the point gene mutation is on the C locus for tyrosinase, an enzyme responsible for melanin production. This is the same locus for complete albinism. It is shown with the sign cs, and needs two alleles of cs for the points to be expressed.
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