Hormone assay is the production of pure forms of hormone. Human genes for insulin, somatostain, thymosin, human growth hormone have been cleaned to produce pure forms of these biologically important fine chemicals or hormones.
In 1984, a functional gonadotropic hormone was also obtained from transformed human cells.
For natural gene cloning of human insulin gene in E.coli the following steps are included.
Human pancreas cells are broken, releasing many RNA.
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These are separated from the rest of the cell material using high speed centrifugation technique.
Insulin in RNA is isolated by northern blotting.
The enzyme, reverse transcriptase, is added to the in-RNA along with the primer DNA.
Using m-RNA as a template double stranded DNA is obtained. This is called complementary DNA (cDNA).
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cDNA for insulin is now introduced in plasmid (the cloning vector) of E.coli.
Plasmid is now introduced in the bacterial cell. A single plasmid inside E.coli can multiply to yield its several copies which may be even a few dozens.
Thus several copies of insulin gene are also produced which multiply with the bacterial multiplication. Thus a clone of bacterial cell with gene for human insulin is formed.