Q.Dolly, the sheep was obtained by a technique known as a) Cloning by gene transfer b) Cloning without the help of gametes c) Cloning by tissue culture of somatic cells d) Cloning by nuclear transfer

Cloning produces genetically identical individuals, occurring naturally through asexual reproduction or artificially via nuclear-transfer techniques in the lab. Dolly the sheep (1997, Ian Wilmut and Keith Campbell) was the first mammal cloned, and the first cloned from a differentiated adult somatic cell rather than by fertilisation, exploiting totipotency. The procedure fused a starved, dormant udder cell from a donor ewe with an enucleated egg from a second ewe, then implanted the resulting embryo into a third, surrogate ewe; of 277 attempted fusions only 29 embryos were viable enough to implant, and just one, Dolly, was born — reflecting how inefficient the technique is (over 90% of cloning attempts overall fail). Cloning can aid clinical trials, drug/protein production, stem cell research and conservation of endangered species, but carries real downsides: it is slow and expensive, can cause animal suffering, produces surrogates and offspring with higher rates of adverse health outcomes and mortality, tends to make cloned animals age faster and be less healthy (as Dolly herself showed), can trigger genetic disorders, raises unresolved questions about eating cloned-animal meat, and concerns bioethicists as a potential threat to biodiversity and natural evolution. A related technique, the gene 'knockout', deliberately disables one or more of an organism's own genes to study its normal function.