Animal Cloning

Cloning is the production of genetically identical individuals of an organism, occurring naturally through asexual reproduction or artificially in the laboratory; in biotechnology specifically, cloning can refer to whole-organism cloning or to molecular cloning of individual cells or DNA fragments. Dolly the sheep, produced in 1997 by Ian Wilmut and Keith Campbell, was the first mammal ever cloned, and the first animal cloned from a differentiated adult somatic cell rather than from fertilisation. The procedure exploited totipotency — the ability of a single cell to redevelop into an entire organism. Mammary-gland (udder) cells were taken from a donor ewe and starved for five days, which stopped their normal growth cycle and pushed them into a dormant, totipotent-like state; separately, an egg was taken from another ewe and its nucleus removed to leave an enucleated ovum. The dormant udder cell and the enucleated egg were fused, the mammary cell's outer membrane was ruptured so the egg's cytoplasm could envelop its nucleus, and the resulting fused cell was implanted into a third ewe acting as surrogate mother; five months later, Dolly was born, genetically identical to the udder-cell donor. In practice the technique is extremely inefficient — of 277 fused cell attempts, only 29 embryos were viable enough to implant, and just one, Dolly, was born, and more than 90% of cloning attempts overall still fail to produce a viable offspring. Cloning offers real benefits: it can aid clinical trials and drug/protein production, supports stem cell research, and could help preserve endangered species. But it also carries serious downsides — the process is slow, expensive and can cause suffering in the animals involved; surrogate mothers and cloned offspring have shown adverse health outcomes and higher mortality; cloned animals (as Dolly herself demonstrated) tend to age faster and be less healthy than a normally bred animal; cloning can trigger genetic disorders; consuming meat from cloned animals raises unresolved human-health questions; and animal-rights and bioethics a …