The first misconception about biological cloning that I’d like to clear up is that cloning is not the duplication of an existing person. For that you need malfunctioning Star Trek transporter technology (i.e. Star Trek: The Next Generation “Second Chances” where it is revealed that Riker had been duplicated in such a manner).
In real life there are three types of cloning: Monozygotic Multiple Births, Embryo Twinning and Somatic Cell Nuclear Transfer. And, before I lose everyone with my polysyllabic words, I want to stress that the last method is the only way of cloning someone after birth and the clone will never be identical to the original because they will always be younger.
Monozygotic Multiple Births
Nature’s way of cloning. This genetic occurrence at its most likely (i.e. Twins) has about three chances in a thousand of occurring in a normal pregnancy. The resulting offsprings are identical genetically, but can develop to look different through being exposed to different environmental influences. For example, identical twins grow up to have different finger prints.
Embryo Twinning
What nature doesn’t do naturally, can be induced. A fertilised egg begins to divide into more and more cells on its way to becoming an embryo. At this early stage (about six or eight cells) specialisation of the cells hasn’t occurred and by literally tearing the tiny mass of cells into two pieces genetically identical embryos will form. This technique is currently used in IVF programs to increase the number of viable embryos that can be used for fertilisation and I see no reason why this process couldn’t be repeated as required. This is how I see Boba Fett’s genetic makeup being transformed into a army of clones in Star Wars.
Somatic Cell Nuclear Transfer (SCNT)
Here we have the cloning most commonly referred to in fiction. This process is where a Somatic Cell (a cell with a specific bodily function) is used to create a clone of an individual. Simply stated, this technique takes advantage of the fact that every cell in the body contains the DNA for all aspects of the organism despite the fact that only certain parts of that DNA were used in creating that specific cell. The process involves placing the nucleus of a somatic cell within an egg of the same species which has had its own nucleus removed. If this process is successful the resulting individual will be genetically identical to the individual. The first successful mammalian clone created using SCNT was Dolly the Sheep in 1996 (see reference below).

The Preserved Remains of Dolly the Sheep: Cloned 1996, died 2003.
Image is in the public domain courtesy of Llull via WikiMedia Commons
Of course these techniques of cloning were all part of fiction well before Dolly made her first bleat. Prime examples are Aldous Huxley’s “Brave New World” and Ira Levin’s “Boys from Brazil”. SPOILER ALERT: In “Brave New World”, Embryo Twinning is used to create the large numbers of lesser caste humans needed to support the ruling elite. And the boys of Ira Levin’s “Boys from Brazil” are SCNT clones of Adolph Hitler. END SPOILERS
Now, back to my bugbear of cloning being used as a way of creating an exact duplicate of an individual. With the SCNT technique there are a number of reasons why the clone might not be identical to the cloned, apart from the obvious age difference.
1. Environment
As mentioned above, the environment the clone is exposed to while growing up to will dictate some of its physical and mental characteristics. As this occurs in Monozygotic Twins have (i.e. As adults they have different finger prints) there is no genetic reason why a clone should also not diverge from the cloned other given different growing conditions.
2. Mutations
With SCNT clones there is also no guarantee that the genetics of the Somatic Cell used to create the clone were exactly those of the cloned individual. The cell used for the cloning may be a healthy example of that type of cell, but as only part of the DNA it contains is active there is no way of ensuring that there aren’t mutations in the unused part that won’t become apparent until the entire genome of the individual is recreated in the clone.
3. Possible Reduced Life Span
There is a limit to the number of times the cells of the body can duplicate themselves. This limit is based on segments of inactive DNA called Telomeres that cap the end of a chromosomes DNA strains and are reduced by successive replications. When these Telomeres disappear the strands of DNA start to unravel and the cell starts to fail to duplicate properly and will eventually die of old age.
Although experimental results indicates this is not always the case (see references on Telomeres below), it is possible that a SCNT created clone’s chromosomes are based on DNA that has already used up a significant length of their Telomeres. This would mean that the clone’s cells would have fewer replications available to them before they started succumbing to the symptoms of old age.
4. Different Mitochondrial DNA
This is a subtle one, but one that could be very useful both in fiction and reality.
Mitochondria are organelles (specialised sub-units of a cell with their own DNA) found within all cells. Mitochondria are passed from mother to offspring through the fluid surrounding the nucleus in the egg and have nothing to do with the DNA of the cell’s nucleus or the father of the child. Therefore, the clone will have mitochondria with the DNA of the host egg, not the cloned individual and therefore be identifiable as being different from the original in most cases. The exception to this would be the SCNT clone of a woman made from her own egg or a close female relative. In this case the Mitochondrial DNA should be identical.
Well, that’s the basics, so I want all you writers out there who don’t know what they’re talking about to stop cloning about with this stuff ;-)
Until next time. Keep writing.
Phill.
References:
About that malfunction Star Trek Transporter
http://en.wikipedia.org/wiki/Second_Chances_(Star_Trek:_The_Next_Generation)
Dolly the Sheep: the first mammal successful cloned using Somatic Cell Nuclear Transfer
http://en.wikipedia.org/wiki/Dolly_the_Sheep
Telomeres, knowing when to stop
http://en.wikipedia.org/wiki/Telomeres
All about Mitochondria
http://en.wikipedia.org/wiki/Mitochondria
The Wikipedia on Cloning
http://en.wikipedia.org/wiki/Cloning
N.B. Please note that I although I use the Wikipedia (and WikiMedia Commons) a lot for references, this is for expediency and the familiarity of my readers. Anyone interested in further studies should make use of the references where available and understand that the Wikipedia is a co-operative project contributable to by anyone and must always be looked at in that light.






