What is cloning?

What are the methods/techniques of cloning?

• I found many results including: somatic cell nuclear transfer, artificial twinning, reproductive cloning, therapeutic cloning and gene cloning....which ones are right? I need to write a paper and dont understand which ones are correct. Thanks in advance!

• Answer:

  The dairy industry uses embryo splitting as a form of artificial embryo twinning. This is blastomere separation (were they tease the egg's first cellular divisions apart to produce twins). Cloning a gene is usually based on making a reverse transcribed cDNA copy from the mRNA. Placing this in an expression plasmid and transfecting it into a cell line for protein production in culture. The protein can be isolated from the growth media and used as a drug. The technique used to create 'Dolly' was somatic cell nuclear transfer (SCNT), the technique where the nucleus of a somatic cell is injected into an enucleated egg cell. Traditionally the nucleus would be placed in a series of eggs until the zygotes were able to completely remove the regulations and produce a functional embryo. This is sometimes called reproductive cloning.