

How Tortoiseshell Cats Show the Limits of Cloning - barredo
http://io9.com/5890039/how-tortoiseshell-cats-show-the-limits-of-cloning

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Groxx
So, in summary, we can't clone tortoiseshell cats because we can't clone their
_patterns_?

In that case we can't clone anything - identical twins don't have identical
fingerprints.

This also ignores the problem of "active" chromosomes (even though it relies
on it). Well sure, you'll get one that's active, and that can't be used
directly to clone a tortoiseshell cat into another tortoiseshell cat - but
that will only be true until we can reactivate the inactive one.

A cursory glance through Wikipedia suggests X-inactivation isn't a well-
understood area of genetics, so I propose it's not an _actual_ limit, but that
it lies beyond our current "limit of understanding". Calling it impossible is
pure conjecture, but probably makes for a more link-baity article.

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masklinn
> Calling it impossible is pure conjecture, but probably makes for a more
> link-baity article.

It's probably right though, and would be received with an incredulous "well
duh" by most (if not all) biologists: we've known for quite some time that
there's a certain amount of plasticity in development.

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coroxout
"Even if someone were to nab a cell from a developing embryo before the
X-linked inactivation happened, the new cloned kitten would also randomly
inactivate its X chromosomes, leaving two cloned siblings that don't have the
exact same color pattern."

The different colour patterns part is true for any cloned cat's markings, not
just clones of a tortoiseshell.

The cloned cat "Cc" who hit the news a decade ago was a tabby-and-white clone
of a calico cat; calico patterns also result from having the black coat gene
on one X chromosome and the ginger coat gene on the other, which is why calico
and tortoiseshell cats are almost all female, and why ginger cats are three
times more likely to be male than female. Trisomy does occur in cats but very
rarely.

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mikecane
So randomness is an inherent guaranteed feature of life itself. Imagine if
this applied universally to skin color too. What would our prejudices be then?
Cue 1960s _Star Trek_ episode where one guy is white on left side while the
other is white on his right side...

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noonespecial
I've always thought it would be teh awesome to be a calico human, if for no
other reason than I could snort derisively at human racism.

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DrJokepu
I can't help but be reminded of the various copy protection schemes they used
with CD/DVD disks, such as SafeDisc. It feels like this is "nature's copy
protection scheme", if you forgive the cliché.

~~~
rsynnott
Somehow, this is a terribly amusing comparison.

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JumpCrisscross
We're still working with the primitives, the biological equivalent of machine
code. Even when we get to genes we're talking about pre-defined functions
which call external libraries (the epigenetic and environmental factors) that
we are limited to splicing around.

The quantum shift will come when we are able to abstract the genetic and
epigenetic functions. The metaphor has yet to shift.

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gojomo
I think the io9 author is striving here to emphasize a favored, romantic
conclusion: "No matter how advanced the technology, there is no way to clone a
certain kind of animal. Life is sometimes determined to be unique, in spite of
our best efforts to make it predictable."

I expect it's equally likely a way to reset the X-linked-inactivation within a
single cell will be discovered, so while the coloring of the clone won't be a
perfect copy, it will be a product of roughly the same random process as the
template cat. (Perhaps the reset would even be possible in adult cells: give
your cat a pill to rescramble its colors over the course of a shedding cycle,
or force it one way or the other.)

Of course there are all sorts of other confounding influences, such as
horizontal gene transfer and chimerism, both of which will probably turn out
to be more important than usually assumed. But given a few hundred years, the
error in 'cloning' an organism can likely be made almost imperceptibly small.

~~~
Zimahl
> I expect it's equally likely a way to reset the X-linked-inactivation within
> a single cell will be discovered, so while the coloring of the clone won't
> be a perfect copy, it will be a product of roughly the same random process
> as the template cat.

That's not the point of cloning, though. Scientists expect an exact replica -
without that, what's the point? I can find you another tortoise shell cat that
looks _almost_ exactly the same in the real world, sans an expensive
procedure. What you'd want is an exact copy of your beloved cat. I think what
the article hinting at, but not saying, is that if something as simple as a
hair pattern can't be copied then other more complicated systems, for example
the brain, certainly have similar inconsistencies that arise during the
cloning process.

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Groxx
Scientists don't value duplication unless it's also visually identical? This
is a new bit of information to me. The people this likely matters the most to
are people trying to clone their pets.

As for non-copyable attributes, we've known that for a long time - twin
fingerprints, for instance. This discovery hasn't caused all funding for
cloning to be withdrawn, so I doubt it matters as much as you seem to be
implying.

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tdicola
Torties are great, loyal cats--they can have a bit of an attitude though. :)
Here's my little tortie girl: <http://i.imgur.com/ilSqNl.jpg>

~~~
Zimahl
Beautiful cat. I have a dilute calico female that is very sweet, but only to
me and my wife. I think this might be more indicative of female cats in
general. I find more than 1 female in a home is typically a problem, whereas
multiple (neutered) males tend to get along better.

If I remember correctly, with the exception of genetic anomalies,
calicos/tortoise shells are always female and orange tabbies always being
male. The other interesting thing I read was that the more white on a calico,
the larger the individual color 'splotches'. A calico with no white will have
the black and red mixed all over (like your cat).

