Posted by
timothy
on from the no-two-cats-are-alike dept.
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:Nature vs. Nurture
by
ishark
·
· Score: 5, Informative
The coats are different colors. How is this possible?
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 and even more here.
Like everything else in the news about cloning, the article completely passes over the science.
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
by
one9nine
·
· Score: 4, Informative
Mod parent up, finally the correct explaination.
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:so it is not a copy cat?
by
kirkjobsluder
·
· Score: 4, Informative
One thing that you "don't do" is clone clones.
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:
Re:so it is not a copy cat?
by
kirkjobsluder
·
· Score: 3, Informative
What do you mean by developmental noise? How is that distinguishable from environment? And do other parts of the genome and its phenotypes constitute an environment for a particular gene?
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?
by
Daetrin
·
· Score: 4, Informative
You're confusing apples with oranges, or perhaps bananas with oranges:)
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.
Slashdot Mirror
The coats are different colors. How is this possible?
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
and even more here.
Like everything else in the news about cloning, the article completely passes over the science.
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.
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.
One thing that you "don't do" is clone clones.
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.
What do you mean by developmental noise? How is that distinguishable from environment? And do other parts of the genome and its phenotypes constitute an environment for a particular gene?
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.
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.
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