Cloning - Not Ewe Again
We've discussed where cloning came from, but where is it going?
Last time, I talked about the history of cloning, and how, after 30 years, the early pioneers had worked their way up from producing amphibians like frogs, to mammals like cows. The scientists did this by transplanting the cow DNA into the fertilised egg from another cow, after its original DNA had been ripped out. You can think of the DNA as the blueprint for an animal or plant. But there was always a problem - this technique of transplanting the DNA worked only when the DNA came from an immature cell.
It never worked when they took the donor DNA from an adult cell. That's why there was so much excitement, in February 1997, when the Rosalin Institute in Scotland announced the birth of Dolly the sheep. She was the first clone to come from a fully specialised adult cell. The donor DNA came from cells from the udder, or mammary gland, of a sheep - and so she was called Dolly, as in Dolly Parton.
As an animal matures into a full adult, its cells become more specialised. So how did the Dolly team make the fully-specialised mammary cells go back to a primeval state? They tricked the cells by putting them on a near-starvation diet. Normally mammary cells will divide and then grow, and then divide and grow, and divide again - but always into more mammary cells. But when the food supply is short, they don't divide any more. Somehow, and we still don't know how, the near-starvation diet makes the mammary cells forget that they are specialised mammary cells. A long hunger seems to send sheep mammary cells back to an earlier unspecialised state. And once they were in this unspecialised state, they could then turn into all the cells that make an adult - cells such as liver cells, nerve cells and of course, mammary cells.
But don't let me give you the impression that cloning Dolly, the sheep, was easy. The scientific team at Roslin had some 400 attempts to transplant the nucleus from the adult mammary cell. Only some of the eggs got successfully fertilised by this adult DNA. They were each implanted into the uterus of another sheep. But there were 28 miscarriages, and only one, the famous Dolly, survived to grow to adulthood.
But if you think that cloning sheep is hard, humans are much harder, especially with the meagre knowledge that we have today. In fact, when you look at how we humans turn fertilised eggs into babies, you'll see that the process is very inefficient. One study looked at fertile women who were trying to get pregnant. The scientists examined their blood for a chemical called beta-HCG. Beta-HCG appears in the blood when a woman is pregnant. In 80 percent of cases, the foetus spontaneously aborted soon after fertilisation, and was washed out in the next menstrual blood flow. The women did not even know that they had been pregnant, and that the embryo had died.
At the moment, the research into cloning is kind of like doing a backwards version of Frankenstein's monster, where various human organs and body parts were stitched together to make the monster. But current cloning research is heading the other way. It wants to clone cells from a human, so that we can grow various organs and body parts for transplant.
The aim of this research, at least over the next ten years, is to clone any organs or body parts that you might need, from your own adult cells. They would take a cell from the inside of your mouth, take out the nucleus or DNA which is your own personal blueprint, and somehow use that as a trigger to grow more organs. The trick lies in that somehow.
Nobody wants to work with embryo cells in the long-term. They are too hard to get hold of, too fragile, and fraught with ethical problems. But in the short-term, the scientists have to work with the embryo cells to learn how to make the DNA from adult cells produce any organ we want.
But let's look further ahead. Once we learn how to clone an entire human being, could somebody clone you, without your knowing about it? Maybe you're so wonderful that an ex-girlfriend or ex-husband who's still in love with you wants to have their own personal copy of you. Well, it would be pretty easy to clone another you without your knowing about it.
There are lots of body tissue samples around. For example, the Armed Forces Institute of Pathology in Washington DC has a huge tissue bank that forensic scientists and pathologists use. It has about 92 million tissue samples from people around the world.
And every time you've given blood, you've given away some of your precious DNA. Blood samples are taken from newborn babies to screen for diseases such as hypothyroidism. These blood samples are sometimes stored for years or decades.
And if somebody who is hopelessly in love with you can't get your body tissues from a regular pathology institute, they could always try stealing some of your saliva from the cutlery that you left behind in your favourite restaurant...
Published 30 August 2000
© 2013 Karl S. Kruszelnicki Pty Ltd