Human Health - Cloning

The process of producing an exact genetic replica of a cell, tissue, organ, or entire organism is called cloning.

or

Cloning is the process of producing identical copies of a gene, DNA fragment, cell, or organism.

The production of a complete organism by fusion of a somatic cell nucleus with an enucleated ovum is called reproductive cloning.

The technique of producing stem cells from cloned embryos for treatment of diseases is called therapeutic cloning.

Gene cloning is a genetic engineering technique in which a single copy of a gene or DNA segment is isolated and multiplied to produce many identical copies.

• Cloning = producing an exact genetic copy of a gene, cell, tissue, or organism.
• Dolly the sheep (Finn Dorset) was the first mammal cloned from an adult somatic cell, born on 5 July 1996.
• Created by Sir Ian Wilmut and Keith Campbell at the Roslin Institute, University of Edinburgh, with PPL Therapeutics.
• Technique used: Somatic Cell Nuclear Transfer (SCNT) – nucleus from a mammary cell inserted into an enucleated egg from a Scottish Blackface ewe; a third ewe served as surrogate.
• Publicly announced on 22 February 1997, alongside the research paper – sparked global ethical debate.
• Significance: proved an adult differentiated cell can revert to a totipotent state to form a whole new organism.
• Note: Earlier sheep clones (1984, and Megan/Morag in 1995) used embryonic cells – Dolly was unique for using an adult cell.

Dolly holds historical importance as the first mammal cloned from the nucleus of an adult somatic cell. Her creation demonstrated that a fully differentiated cell could be used to generate a complete new organism.

Steps Involved in the Process

1. A somatic (body) cell was taken from the donor sheep.
2. An egg cell was collected from another sheep.
3. The nucleus of the egg cell was removed – a step known as enucleation.
4. The nucleus from the somatic cell was inserted into the enucleated egg.
5. The reconstructed cell was stimulated to begin dividing, forming an embryo.
6. The embryo was implanted into the uterus of a surrogate mother.
7. The surrogate mother gave birth to Dolly, the cloned offspring.

This sequence illustrates the technique known as somatic cell nuclear transfer, which remains the foundation of most reproductive cloning research.

Cloning has several practical and research applications, including:

• production of medically useful proteins through gene cloning, such as insulin, somatostatin, erythropoietin, factor VIII, interleukin, and interferon.
• development of stem-cell-based therapeutic approaches through therapeutic cloning.
• research into cell differentiation, development, and heredity.
• potential preservation or multiplication of desirable traits in selected organisms.

Cloning therefore carries strong scientific promise but must be approached with caution due to its ethical and technical complexities.

• Cloning is the process of producing an exact genetic copy of a gene, cell, tissue, or organism.
• Gene cloning isolates and multiplies a single DNA segment to produce medically useful proteins.
• Reproductive cloning fuses a somatic cell nucleus with an enucleated egg to produce a complete organism.
• Therapeutic cloning derives stem cells from cloned embryos for disease treatment and medical research.
• Dolly the sheep was the first mammal cloned from an adult somatic cell using somatic cell nuclear transfer (SCNT).
• Cloning is associated with low technical efficiency, health abnormalities in offspring, and significant ethical concerns.