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After the process of construction we go for screening process of selecting a recombinant host. Which includes:

  1. DNA hybridisation
  2. Colony hybridisation
  3. Random primer labeling
  4. Nucleotide autoradiography

These techniques are very tedious. So instead of all these tedious process why cannot we just grow them in a minimal media to get the recombinant host and to check which protein is formed?

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  • $\begingroup$ I have edited your title, first because you should avoid abbreviations in titles and second to improve the English. However I must say I don’t understand what you mean by “recombinant host”. By host we usually mean the organism (bacterium etc.) in which we are propagating some vector (plasmid, phage etc) carrying the DNA. I advise you to set out the problem in more detail, step by step, and this will clarify the question and perhaps provide the answer. $\endgroup$ – David Aug 26 '16 at 22:01
  • $\begingroup$ 1.) What organism are you referring to? A genomic DNA library from E. coil would be much smaller (have far fewer unique genomic fragments) than a genomic library from a vertebrate (all other things being equal). So the genomic library you wish to screen for your favourite gene may have between thousands, and millions, of unique inserts. Screening those for protein production, as you suggested, could also be tedious. 2.) Are you dealing with a prokaryote or a eukaryote genome? Many eukaryotic genes contain introns, which need to be removed by splicing, so a library of genomic clones $\endgroup$ – mdperry Aug 27 '16 at 0:43
  • $\begingroup$ from a eukaryote would be quite unlikely to produce a protein during propagation in a prokaryotic host. If, on the other hand, you are dealing with a cDNA library, then there are expression vectors designed to express the foreign recombinant proteins. But how do you propose to identify the protein or interest? $\endgroup$ – mdperry Aug 27 '16 at 0:49
  • $\begingroup$ The protocol makes sense, if you require to have access to a physical copy of the genomic DNA sequence - and you do not have sequence information about the genomic DNA (or even your probe of your interest). While sequencing service provides will nowadays likely use fluorescence rather than autoradiography, it is wrong to consider the protocol tedious, as you screen many different colonies at the same time with few experimental steps. Selection through media would only make sense, if you already knew what your gene is doing, and you had introduced a cognate inducible mutation in the host. $\endgroup$ – tsttst Aug 27 '16 at 3:26
  • $\begingroup$ Actually my question was, in g dna library we do alot of screening process just to find if the transformation process is successful or not. Instead of that why we cannot grow the sample in a minimal media, we can quickly find the transformed bacteria. $\endgroup$ – Ashwin.N Aug 27 '16 at 6:34

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