1411957
story
bbsguru writes
"When Texas A&M researchers announced the first Cloned Kitty about a year ago, everyone expected to see a Multiplicity-style pair of cats by now. Not so! The clone is genetically identical, but in many other ways totally a different cat. This
CNN Story has details."
Re:why on earth would you expect a carbon copy ? (Score:2, Informative)
Alfred Einstein [mozartproject.org], Albert's brother, was a very influential, and quite brilliant, musicologist.
Re:Nature vs. Nurture (Score:5, Informative)
The color of a cat's coat is a much more complex matter than what it seems. While, of course, genetics applies, there are a lot of "minor" details which are not completely understood.
Even in "purebreed" cats you can have a lot of fluctuations in the fur color (there are lots of variations in the "blue" you can see in the Chartreux). While some of them are genetically transferred (and thus selective breeding can enhance/cancel them), for some of them the situation is not so clear, an example being the tortie-shell females (black/red or blue/cream), where the distribution of the color doesn't seem much controllable. From what they show with Cc it also seems that the tabby stripes can show up more or less depending on the individual.
Some more info on the main cat color genes can be found here [fanciers.com]
and even more here [netpets.com].
ST:TNG Episode "Second Chances" comes to mind (Score:2, Informative)
Re:so - what's the truth about identical twins (Score:1, Informative)
Embryonic development is not chaotic; it's a cat, not a cancer. In fact, for a small animal such as C. elegans, the history is every single cell in the animal is known. This is not so for larger animals for practical reasons (ie. size, lack of transparancy, growing in womb etc), but that doesn't imply chaos.
Re:Nature vs. Nurture (Score:2, Informative)
Calico is mostly a female only gene, the odd male that is born a Calico is usual sterile.
I'm surprised they chose a Calico to clone. It's possible because a Calico needs a certain set of genes, most recessive, and they might have been easier to isolate.
Re:Extremely Interesting (Score:5, Informative)
I doubt that very many developmental biologists are shocked by the clone having a different color. Even if the cat embryos went through the exact same conditions in the womb, there are some parts of biological development which are, basically, random. (The way that human visual sensors map to the visual cortex in the back of the brain is random and bizarre). Even if Cc was carried by Rainbow's mom, its unlikely that the mother cat followed the same sleep cycle, ate the exact same catfood, experienced the same environmental conditions (from temperature to gravitational variations), etc.
It also brings up interesting evolutionary questions, i.e. if an organisms shape/color/behavior isn't completely determined by genes how, exactly, does this effect how evolution takes place?
Evolution is random to begin with, so you have to consider the averages. It's not literally that Bob the Tortise has a longer neck so it eats more of the food and Dave the Tortise dies. Given a set of genes common to a certian group (Bob's family), even with some random variations, that group could, more often than not, fare better than another group with a different set of genes (and random variations around those genes). So eventually Bob's group does better and those genes permeate the gene pool. Random phenotypical (outward characteristics as opposed to genetic characteristics) variation won't be passed on, so if it gives a particular individual some advantage, good for them, but it doesn't effect the population. If the phenotypical variation is harmful and the creature's genes don't give it enough advantages to keep up, that individual won't pass it's genes on as much as the rest of the population, so they become less common.
And cultural adaptation is a whole nother matter, although you could look at it in a natural-selection context. Will our culture be able to adapt to it's surroundings well enough to avaoid getting killed by other cultures, or from within, or by destroying the habitat? And if our culture as we know it is destroyed, is that just a radical mutation, similar to the way that a few drug resistant bacteria can survive a penicillin dose and breed a new drug-resistant strain?
But that's a different discussion.
Look at the photo! (Score:5, Informative)
First, the cat's color pattern was decided by individual skin cells very early in embryonic development. The individual cells multiply, carrying the same color, to become the pattern on the adult cat.
Second, and most notably, calico cats (tortoise shell) carry a color in each sex chromosome - that's why 99.9% of calico cats are female (XX female, although there are some XXY male calicos but they're sterile). Fur color depends on which X chromosome is active, and which one is inactive (curled up, as they say)
So, looking at the picture, you'll notice the clone (cc) has only two colors indicating that it is not only a clone of the donor cat, but a 100% exact genetic clone of ONE cell of the donor cat. The other X chromosome is completely inactive.
That's just my observation from the photo because no news article will ever talk about the science behind the hype.
Re:Nature vs. Nurture (Score:2, Informative)
But it is thought that Cc (since she is cloned from the genetic material of a single cell from an adult) has the same X chromosome inactivated everywhere. That would explain why she has only two colors of fur.
Female humans also have X inactivation, but I guess the results are not as immediately obvious.
Also, it's generally true for all animals that some genes on the X escape inactivation. Dunno why.
Re:Look at the photo! (Score:2, Informative)
Probably not 100%. Mitochondria have their own DNA, and the mitochondria come from the egg cell that Cc developed from. But they probably did not take the unfertilized egg from Rainbow, since this is a very significant surgery to do on a (still living) cat.
Re:Nature vs. Nurture (Score:5, Informative)
Each of these cells, however, has two copies of the x-chromosome. Only one of these is useful.
This is not true, both Xs are perfectly viable. One contains the gene for tan, the other for black. One X gets switched off in each of the cells at random. Then, when each cell divides, the X chromosome that was turned off continues to be switched off in all of the progeny cells. The skin cells that are produced from these cells will express the color of the X chromosome that was not turned off.
The white coloring is caused by epistatis, or the overriding of one gene by another. Also, in some cats, temperature plays a part on which color the coat will be.
Re:why on earth would you expect a carbon copy ? (Score:3, Informative)
Humans usually have uniformly coloured hair on top of their heads--but even then, identical twins with different hair colour are sometimes seen (Lancet 353 (1999) 562). Cats often have mottled, striped, or otherwise nonuniform coats.
The splotches on a cat are the result some rather interesting processes, one of which is described here [216.239.33.100]. Essentially, cats receive genes determining the colour of their coats from both parents. Within the cat embryo at the stage where it contains a few dozen or fewer cells, one set of genes for colour is deactivated in each cell--but it is not necessarily the same set in different cells.
This random deactivation of genes mean that parts of the cat that develop from one cell within the embryo will show orange fur, while bits from other cells may turn up with black fur. Overall, the effect is mottled fur, in a random pattern--just as is seen with Cc.
Mosaicism and color patterns (Score:3, Informative)
There's no way to predict this pattern, so two cats whose parents have different patterns of orange or black fur will always look different, and the clones of any one of these cats would all look different as well.
And while this is a particularly colorful example of mosaicism, it in fact happens in all mammals, so female clones will always express different patterns of X-linked genetic traits.
Cat genetics (Score:2, Informative)
Here [ufl.edu] you can find everything (or more) than you ever wanted to know about the genetic foundations of the feline fur color, including the tortoiseshell variation. The text requires a basic understanding of genetics lingo (homzygous, allele, recessive and the like).
HTML version [216.239.53.100] of the same from Google's cache for those who don't like the
Re:so it is not a copy cat? (Score:5, Informative)
Bwah? At it's base cloning is basically asexual reproduction of an organism. Making clones of clones is something we did all the time back in my misspent youth training to be a microbiologist. It is something I still do by giving cuttings of "shamrock" and sweedish ivy to friends and relatives. Basically for organisms that already propigate asexually cloning is as simple as taking a cutting and giving it a fresh source of food. There is nothing magical in sexual reproduction that insures good copies. In fact, a large number of mutations are known to only occur during sexual reproduction. Overall, somatic-line cloning is preferred if you want a large number of basically genetically identical individuals.
Of course it is obvious that the clone is not identical. A basic equation in quantitative genetics is:
phenotype = genetics + environment + developmental noise.
Re:don't forget muscle memory (Score:3, Informative)
Re:well... (Score:2, Informative)
I think the problem is that people have a tough time considering what "nature" is. Typically when people talk about "nature vs nurture", they talking about what happens after birth..
The original poster mentioned environment - which basically means "anything not contained within the genes"..
We know that embryos are exposed to hormones and chemicals in the womb, to stimulate development - slightly different amounts, in slightly different places, at slightly different times, and you have different outcomes.. technically, this is "environment"... but it could also be considered "nature" (again, if you're talking pre-birth.)
Different levels of hormones affect fetuses in different ways.. for example, the more testosterone a male fetus is exposed to, the higher the chance of homosexuality.. which is definitely a behavioural trait.. again, this is an environmental issue, not a genetic one (the more pregnancies a woman has with a male fetus, the more testosterone she produces in the womb, and therefore her youngest boys have a higer chance of being gay than their older male siblings.)
Re:Look at the photo! (Score:2, Informative)
Each cell has the complete set of DNA. In theory there's nothing stopping the new cat from from having the exact same pattern as the old cat. However, since the pattern has to do with the positioning of the cells and the inactivated X chromosome is random, the probability is very small.
For an excellent discussion of this topic check out this link [rcn.com].
Re: Actually... No... (Score:3, Informative)
In animals, gender is determined by X and Y chromosomes. The valid choices are XY (male) and XX (female). Other cases create a sterile or nonviable mutant.
Now, cells only require one X chromosome to operate. In females, therefore, every cell de-activates one of the two X chromosomes during fetal development, which becomes a Barr body and is completely genetically useless.
In cats, Black and Brown hair colors are stored on the X chromosome. Thus males can be black or brown (since they have only one X chromosome), and females can be black and brown.
Females get to be black and brown when one inherited X chromosome is black, and the other is brown. Then, when one of the chromosomes is turned into a Barr body, the patch of skin that develops from that fetal cell becomes either black, or brown. Other cells could have disabled the other chromosone, leading to splotches of other colors.
And now for the cloning:
When the ovaries/eggs develop, each egg receives one of each pair of chromosomes. Thus, the eggs of a Brown/Black cat are either Brown, or Black. I am not sure what technique exactly was used in producing the clone, but if they doubled the chromosomes in each egg, the Black egg would create a Black/Black clone. If they merged two eggs together, its possible that they just happened to pick two Black eggs. If they picked a non-egg cell (unlikely) then they would have either had to swap the Barr body for a real X chromosome (in which case they could have chosen a Black/disabled cell, and added Black in again) or somehow re-activate the Barr body.
Re:so it is not a copy cat? (Score:4, Informative)
In part, developmental noise is a "none of the above" for variance that can't be explained in other ways. On the other hand, gene expression and protein production is probablistic. This adds another source of variance. It is never as simple as "Trigger X present, make Y".
So for example with calico cats even with twins born from the same litter there will be variations in coat patterns due to the random deactivation of x-chromosomes.
Re:so it is not a copy cat? (Score:5, Informative)
The original comment was that copying a copy is bad, because errors will accumulate. That's only true if there are errors in the copying process. Assuming you can extract the DNA without damaging it, and inject it into the egg cell without damaging it, then there will be no more errors than there are in naturally grown organisms, which is damn few.
The reason there are so few errors in natural cloning is _why_ (the cloned variety of) Bananas are in danger. They are such perfect copies of each other that they are failing to adapt to a changing enviroment. A sudden change in enviromental conditions are a bacteria or virus that figures out how to take advantage of that stability could theoretically kill every Banana of that variety on the planet.
In that particular case having more genetic drift would be a good thing, but it just doesn't happen very fast with clones, which is why cloning a clone is perfectly safe as long as you're carefull about the original DNA extraction.
As in most things, extremes are bad. No genetic change means you don't adapt to the enviroment at all, and sooner or later changing conditions or something that _does_ adapt will wipe you out. Too much genetic change means that the entire species will either mutate themselves to death or run head-on into an evolutionary dead-end.
Re:so it is not a copy cat? (Score:2, Informative)
Yeah, this is probably redundant, I'm probably not the only one who felt like weighing in.
Re:Well DUH (Score:3, Informative)
Identical twins are that - identical - as much as you treat them differently you can look at them and see the resemblance fairly instantly. These two cats -look- like any two random cats. You wouldn't even pick them as parent and child.
You'd expect a clone and its 'parent' to act differently, sure, but the point that Hollywood wants you to believe is a clone will 'look' identical.