Why can't we simply insert any gene into bacteria and have them create the...

If we want to express the gene in bacteria to make a protein, the gene must point in the right direction relative to the promoter, or control sequence that drives gene expression. If the gene were backwards, the wrong strand of DNA would be transcribed and no protein would be made. In other cases, bacteria may be used as protein factories. If a plasmid contains the right control sequences, bacteria can be induced to express the gene it contains when a chemical signal is added. Expression of the gene leads to production of mRNA, which is translated into protein. Scientists add foreign DNA sequences to bacteria for two reasons: To make it easier to work with the DNA sequence. Once inside bacteria, a stretch of DNA can readily be copied and its sequence determined. To make a foreign protein within bacteria.

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