This follow-up page covers health and other issues of cloned mammals and follows Ruth’s article questioning whether people should clone their cat, even if they could afford it.
I think it is useful to briefly look at the difficulties of cloning cats. This of course is ignoring the seeming impossibility of cloning a cat’s personality. I think that aspect of cloning itself is enough to question the process and is the main point raised in comments to Ruth’s article. It is worth noting that the first cloned cat was a female calico cat (“CC”), who looked very different to her mother. The color and pattern of coats of cats are not exclusively dependent upon the genes of the cat.
In 2002 survey published in the science journal Nature Biotechnology, it was found that in animals cloned through what is called nuclear transfer (transplanting the nucleus of one cell into another), almost a quarter of all cloned mammals failed to reach healthy adulthood. In addition, the survey showed that the health problems in cloned animals were wide-ranging from mild to fatal and included1:
- Heart defects
- Liver fibrosis
- Respiratory failure
In 2003 the first cloned mammal, Dolly, a sheep, was euthanised because of a lung tumour. It was caused by a virus. Although, in defence, it was said that there was no evidence that the cloning was a factor in the disease.
In addition to those mentioned above, health problems are2:
- Sometimes (scientists don’t know when it will occur): an increase in birth size (Large Offspring Syndrome – LOS). These animals have large organs, which can lead to health problems.
- A variety of defects in vital organs such as liver, brain and heart.
- Problems with the immune system.
- Premature aging. Dolly, the cloned sheep mentioned above died when she was 6 years old, which is about half the average age of the lifespan of sheet. That said, the 1st cloned cat, CC, at May 17, 2011, was 10 years of age. I don’t know how much longer she lived beyond that date. Dolly’s shorter than average lifespan was due to shortened chromosomes because the ends of the chromosomes have shrunk more than usual on cloning (as I understand it).
CC was treated like any other cat by her caretaker, Shirley Kraemer. CC had a litter of 4 kittens one of which was stillborn while no health issues were detected in the remaining kittens3.
Using clones in a breeding program results in inbreeding which in turn increases the possibility of offspring being unhealthy.
When animals are cloned through somatic cell nuclear transfer there is a high failure rate. The success rate ranges from 0.1% to 3%. This means that out of 1000 attempts there may only be one successful clone4.
In natural development, the time at which a gene expresses itself in the appearance etc. of the animal is dictated by the nucleus of the cell, which is programmed. In cloned animals the transferred nucleus does not have the same programming and therefore there is a question mark over whether the clone will express the right genes at the right time? This is still an unknown4.
Are there any conservation benefits in cloning wild cat species? Two African wildcat clones gave birth to cubs in around 2004 at the Audubon National Institute Of New Orleans. It was described as a triumph but I cannot find information about how well the kittens developed. The conservation value is dubious. Dr Lieberman director of WWF’s Species Programme says that cloning has no value for conserving endangered species in the wild. In fact it is a process of failure of conservation in the wild as far as I am concerned. The process seems to be more about scientists experimenting with mammals as an academic exercise rather than having the objective of ensuring the existence of endangered species.