Question on genetic engineering?

Question

I have been given a question that i can't seem to answer. The question is "the bacterium Escherichia coli has been genetically engineered to produce insulin. Briefly, explain why the intron sequences, which occur in the human gene sequence for insulin, were omitted when this gene sequence was cloned into Escherichia coli.

Answer 1

just a thort..wudn't it be easier to harvest mRNA (all the introns wud b spliced out for u) from a healthy pancreas and  use  rev transcriptase 2 copy back to an uninterrupted DNA sequence and THEN insert it into the e. coli plasmids?

OK..there wud b some % transcription errors..but these wud presumably abort?

Answer 2

Well, introns are the parts of the DNA that are inbetween the other parts that code for the insulin protein. They are usually simple repeats that don't code for anything. When the protein is being formed, there are enzymes present in the human cell that cut these unimportant introns out and glue the important bits (the exons) together to make a complete coding for insulin.

Now, E. coli bacteria will not have these special enzymes to cut out these introns, so these parts need to be omitted, otherwise the bacteria will produce a protein with the intron amino acids in it - making the protein produced completely different to insulin.