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October 26, 2006

Cat Cloner Closed & Dog Duplicating Discontinued

Following their cat cloning going-out-of-business sale where they discounted cat clones from 50k to 32k, the pet cloning biotech firm Genetic Savings & Clone announced that they would be closing their doors at the end of the year.

People love their pets, but not enough to clone them. Perhaps the daunting price tag convinced them to go adopt a homeless animal in need instead. Long story short, the company has determined that pet cloning is just not commercially viable just yet. Over the past seven years, they've cloned 5 cats, but only sold two of those.

Just who considers cloning their pets? According to Genetic Savings & Clone's Client Overview, "In general, our clients are intelligent, articulate, and well-informed." That's an innocuous statement if I ever heard one. Imagine this was a bank, and they said that in general, their clients were law-abiding citizens. Sorry, but I had a good chuckle there.

Checking out their website and specifically the cats they cloned, I was surprised that CC, the calico they cloned from Rainbow, did not resemble her genetic donor very much.

CC's genetic donor, Rainbow, is a calico domestic shorthair, while CC is a white and tiger-tabby domestic shorthair. What gives? Shouldn't CC be a calico too? The answer to this question sheds light on a fascinating and less-than-fully-understood issue called "X-linked inactivation."

First of all, calicos are almost always female, which means they have two X-chromosomes (versus the male's XY). One of these X chromosomes contains a gene for orange coat color and the other contains a gene for black coat color (white patches are specified by a different set of genes which are not relevant here).

For reasons which are not fully understood, as the embryo develops, a phenomenon called "X-linked inactivation" occurs, in which one or the other X-chromosome in every cell in the Calico embryo becomes randomly inactivated. If the specific X-chromosome containing the gene for orange coat color becomes inactivated, that cell will go on to produce black coat color (assuming it becomes a coat follicle cell). The inverse is true if the X-chromosome containing the gene for black coat color becomes inactivated.

Given that the inactivation is random, one would expect a very fine distribution of orange and black hairs within the coat, but for reasons which are not germane here, the inactivation occurs in larger patches of orange and black.

"Mosaicism" is the term for distribution of different cell types within a single organism. Mosaicism is three-dimensional, meaning that the inactivation of orange or black-producing genes occurs within cells throughout the calico's body regardless of whether the cells have anything to do with production of the animal's coat. Thus, even the specific cumulus cell used to clone CC would have been inactivated for either orange or black coat color.

If the nuclear transfer process were to reset the inactivated X-chromosome the way it resets the nuclear differentiation, then one might expect to see a calico clone with a calico coat. On the other hand, if nuclear transfer does not reset X-activation then one would expect to see a clone with a black coat if the donor cell used had an orange coat gene on the inactivated X-chromosome, and conversely one would expect a clone with an orange coat if the donor cell used had an black coat gene on the inactivated X-chromosome.

The fact that CC has no orange in her coat is consistent both with the theory that nuclear transfer does not reset X-activation, and also that the cumulus cell used had an orange coat gene on the inactivated X-chromosome.

More at: X-linked Inactivation

While this may explain the scientifics behind this occurence, it probably did not help with the company's business plans and customer satisfaction.

Posted by sorsha at October 26, 2006 10:19 AM