The Science of Cloning

LiveScience has a good FAQ article on the basics of how animals are cloned. Cloning is only going to get more prominent in the future, so it wouldn’t hurt to have an idea of what it is and how it’s done. I won’t summarize it here, since it’s already explained briefly and nicely. The last paragraph mentions the recent successful cloning of a human embryo for harvesting embryonic stem cells, which I discussed a while ago along with some background on stem cells.

As always, feel free to let me know if you’d like any aspect explained in more detail.


“World’s First Cloned Human Embryonic Stem Cells”

From New Scientist: For the first time, scientists have successfully put human adult somatic cell DNA into an unfertilized egg, induced that egg to divide and develop into a blastocyst – a first step towards a fetus – and harvested embryonic stem cells from those blastocysts, containing the adult’s DNA. There was a problem though: they could only accomplish this if they left in the egg’s DNA, so the stem cells have too many chromosomes (humans have 46; these cells have 69). Nevertheless, it’s a first step towards having real embryonic stem cells (as opposed to IPS cells) with adult DNA, which is a big boon for medical research.

If the above didn’t quite make sense to you, here’s some background:

Stem Cells To Date

You may have heard that there are two main types of “stem cells” in play in the research world: firstly, there are embryonic stem cells, which are cells derived from embryos that can potentially differentiate into any type of body cell. As they divide, their daughter cells will have more and more specific functions and more restricted potential, until they give rise to very specific cell types – a particular type of neuron, or a particular type of blood cell, for example. These cells will have varying limitations; for example, a neuron can’t divide – that’s about as limited as a cell can get. An embryonic stem cell has the most potential of any cell type – it can divide into anything. 

This is useful because it means researchers can grow any kind of cell they want in the lab. They can study how everything develops, and they can study, well, anything. There’s also the potential for stem cell therapy – injecting young, healthy cells into an injury to replace injured cells that the body wouldn’t normally be able to – like neurons, which I mentioned above can’t replicate. 

More recently scientists created induced pluripotent stem cells, or IPS cells. Basically they figured out ways of dedifferentiating adult, specialized cells, making them less specialized, less limited. This meant that they could make embryonic stem cell-like cells that would have the DNA of a particular person. In relation to the uses of stem cells mentioned above, this offers the benefits that you can study the progression of a particular disease, for instance; you could take cells from an adult with a known disease, grow their IPS cells in a lab and see where they go wrong, to put it broadly. In terms of stem cell therapy, you could have better odds of injecting cells into a person without having their immune system reject these cells, since they’d be their own body’s cells.

Perhaps most importantly to a lot of people, you can create IPS cells without destroying human blastocysts in the process, which has been and still is a huge source of political controversy regarding embryonic stem cell research. Contrary to what many morality-based advocates of IPS cell research would have you believe though, IPS cells are not the same as embryonic stem cells. They may be very similar and behave in largely the same way, but they are most certainly not the same thing, and there’s no way to possibly prove that they’re exactly the same, even if it were likely. There’s a lasting place for both of them in research; both will prove useful in understanding everything about human life. 

New Stem Cells

Whew, okay. That’s a very, very brief and simplified overview of stem cells-to-date. This new research took a different approach (typically used in cloning): they took the DNA from an adult, specialized cell, and put it into an egg; they then grew that egg into a blastocyst. From the blastocyst, they could extract embryonic stem cells. This method has the benefits of harvesting actual embryonic stem cells, while also having cells with the DNA of a particular adult, meaning they could be used for specialized stem cell therapy and whatnot. 

But not yet. They weren’t able to get the egg to form a blastocyst when they tried to remove the egg’s own DNA; they had to leave it in there for it to develop into stem cells, meaning that with the egg’s DNA and the adult donor DNA, these stem cells had too many chromosomes – they’re not an accurate model of human cells. Of course, now they’re working on figuring out how to get the egg to develop after they take out its DNA; I’m sure we’ll hear about this in the near future, and it’ll be big news.

Once they can make a viable blastocyst with just the adult DNA, it’s not a far leap to actual human cloning: they just have to implant it into a woman and bring it to term. Of course that entails who-knows-how-many years of troubleshooting, but it’s closer now than it’s ever been before. I call dibs on being cloned. 

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