Reproductive cloning

ES cells can also be used to generate an animal genetically identical to a living animal, a process termed reproductive cloning. Reproductive cloning has been used in some species, and has been hotly debated, particularly regarding its potential use in humans. 

Clone, identical cells (with respect to genetic constitution) derived from a single cell by asexual reproduction. Receptors can be cloned into cells by inserting a gene into the cell line a colony of cells results that are identical and all have the expressed receptor. 

Reppert, S. M., Weaver, D. R. 8r Ebisawa, T. (1994). Cloning and characterization of a mammalian melatonin receptor that mediates reproductive and circadian responses. Neuron 13, 1177-85. 

Sendai, Y., Abe, H., Kikuchi, M., Satoh, T. and Hoshi, H. (1995) Purification and molecular cloning of bovine oviduct specific glycoprotein. Biology of Reproduction 50, 927-934. 

We can divide cloning into therapeutic cloning and reproductive cloning. Therapeutic cloning is synonymous with stem cell research. Under proper control and environment, embryonic stem cells can potentially be directed to grow and develop into different tissues that are invaluable for replacing... 

As discussed in Section 4.7, stem cells have the potential to treat medical conditions beyond the scope that can be offered by drugs alone. However, there are many scientific and ethical hurdles to overcome. On the scientific front, stem cell research activities will intensify over the next decade. These challenges can broadly be divided into (1) determining how to develop stem cells into specific tissues and (2) implanting these tissues into the body without rejection by the recipient s immune system. On the ethical front, it is expected that there will be more debates on the ethical issues of stem cell research. Most scientists consent to therapeutic cloning (stem cell research) but not reproductive cloning. The ethical issue of stem cell research concerns harvesting cells from embryos that are a few days old. This action destroys the embryos. Some questions are ... 

In February 1997, the Scottish scientist Ian Wilmut and colleagues at the Roslin Institute announced the birth of a cloned sheep called Dolly in July 1996. They had removed the nucleus from the egg cell of a sheep and replaced it with the nucleus from an adult sheep. Dolly was born from a surrogate mother sheep and is an exact clone of the adult sheep, unlike offspring from the reproductive process, in which the offspring inherits the genes from both parents. 

Reproductive cloning—Production of a genetically exact copy of an individual. 

Fig. 5. In the experiment, carried out by Charles Weissmann and his co-workers, single Qp-RNA molecules (or viruses) from a wild-type distribution (a) were cloned in E. coli bacteria. After rapid multiplication the clones of individual RNA molecules (b) were analyzed and compared by the fingerprint method. Differences were noticed in one or two positions in the sequence. After a further, long period of reproduction (c) the wild-type distribution (d) was found in every clone, that is, the average sequences had become identical again.

Li XC, Giot JF, Kuhl D, Hen R, Kandel ER. Cloning and characterization of two related serotonergic receptors from the brain and the reproductive system of Aplysia that activate phospholipase C. J Neurosci 1995 15 7585-7591. 

DNA serves as a blueprint for the individual, controlling, among other aspects, the production of highly specific proteins. In sexual reproduction, the DNA of the offspring is derived from the DNA of both parents, and so serves as the material basis of inheritance and of evolution. Cloning experiments, from Dolly the sheep onward genetically modified crops the possible treatment of inherited diseases—in these and other ways, an understanding of the chemical basis of reproduction and in-... 

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