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Cloning

Cloning mainly comprise of reproductive cloning and somatic cloning depending on the resource cells used.

Ø  Reproductive Cloning : Use of blastomeres of an embryo to produce more embryos is known as reproductive cloning. This uses the totipotent power of embryonic cells at early stage of development. This technique can be used for multiplication of superior animals at faster rate.

Ø  Somatic Cloning : The cloning of animals received much attention in 1997 and 1998, with the production of lambs and calves by nuclear transplantation of differentiated or immortalized fetal and adult cells into enucleated metaphase || oocytes. Although the technique is not efficient, the ability to clone animals from differentiated cells has changed our understanding of the irrevocable nature of cell differentiation and germline totipotency.

Nuclear Transfer (NT) is one of the more recent biotechnological procedures for cloning, where the nucleous of an oocytes or zygote is replaced with the nucleous of developments have stimulated interest in this technology globally, starting with the highly publicized birth of ‘Dolly’ cloned from the nucleus of a somatic cell. Subsequent successes were reported in severable species of echonomic interest. NT could be useful in multiplying high value transgenic animals, extreme high producers for traits such as milk in dairy animals, specific disease resistance or environmentally adaptable animals and for conservation of wild and domestic species at the verge of extinction. Yet, the success rates of cloning by nuclear transfer remain very low even in the most researched species and require further scientific input to improve the technique.

Success of NT depends upon different steps starting from proper enucleation and reconstruction procedures, obtaining suitably synchronized stage of development of donar embryonic cell/embryonic stem cells/somatic cells followed by fusion of donar nucleus with the recipient cytoplasm. This has to be done in such a way that nucleus introduced into the enucleated, timed and prepared metaphase|| oocytes is capable of re-expressing its entire genome. Susequently, optimum culture conditions are required to support development of the nuclear- transferred zygote to a syage suitable for transfer to recipient animal for completion of gestation.

Failures are not uncommon, resulting from abnormal chromatin of donar cells, inappropriate or incomplete nuclear or cytoplasmic DNA and protein reprogramming, damage during micromanipulation procedures for enucleation and donar nuclear transfer, apart from culture process inadequacies. Hence, there is need to understand intricacies of the cytoplasm- nuclear interactions and to refine the procedures for obtaining donar nuclei at predetermined stage in the cell cycle for optimum success. Research is needed to identify the cell types and conditions most likely to provide totipotent nuclei for transfer.