What is the Success Rate of Cloning?
When Dolly the Sheep was successfully birthed on July 5, 1996, there was a general outcry over genetically engineered animals and humans one day replacing regular animals and people. But that fear has proven to be unfounded, partially due to the very low success rate in cloning. For example, Dolly was the only lamb born out of 277 attempts at cloning.
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Size
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The success rate of cloning animals is (depending on species) 0.1 to 3%. This roughly translates to only one to three cloned animals living to be born for every one thousand cloning attempts. Having that animal live to reproduce is even slimmer. Many cloned animals die within the first few days of being born. Dolly the Sheep was one of the few exceptions. Although she died at a young age of six, she did successfully give birth six lambs in her short life.
Misconceptions
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A cloned animal might not even be a true clone. This means that despite being cloned, the DNA could still go through changes from the original donated DNA. When cells divide in order to make a new creature, they normally go through changes in the DNA sequence. It is so far impossible to produce a cloned animal that is 100% genetically identical to another.
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Considerations
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A cloned animal is made by taking the DNA from some cells out from the donor animal and a surrogate mother animal's oocyte (immature egg cell). The DNA of the surrogate mother is cleaned out of the oocyte. The DNA from the donor animal is replaced inside the walls of the oocyte. This is then transferred to the surrogate mother, who then becomes impregnated with the cell and gives birth in the usual manner.
Types
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There are many ways in which the cloning goes wrong. The egg may not take hold in the surrogate mother's uterus and then it dies. The surrogate's oocyte cell may reject the donated DNA. The cells might not divide properly to make a baby animal. There could be a stillborn or a complication in birth that kills the baby. Cloned baby animals are often prone to large organ syndrome (LOS) which results in a very large baby -- or a baby with inner organs so large that the small body can't survive.
Theories/Speculation
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Due to the very low success rate of cloning, there hasn't been any practical reason to clone animals for medical research or the agricultural business. Only private firms are willing to clone for niche markets like cloning dead pets. Although cloning seems to be a great scientific breakthrough, there have not been actual ways to use it. Cloning entire animals, for now, is a novelty at best. There has been much more success at cloning body parts from stem cell research and that seems to be where cloning science is concentrating its energies for now.
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Resources
- Photo Credit Dolly the Sheep image by Wikimedia Commons
