Why is DNA coding for human insulin used from mRNA and not DNA?

i think it has something to do with introns.

Why is DNA coding for human insulin used from mRNA and not DNA?
Because DNA contains coding sequences, called exons, but also a lot of untranslated, regulatory stretches, called introns.





When a gene is transcribed in the cell, it is transcribed with exons and introns into pre-mRNA. This needs to be exported into the cytoplasm and "processed" into mRNA before translation takes place. mRNA can be transformed into cDNA, which, when artificially transcribed, will give "mature" mRNA which does not need processing.


Recombinant insulin is normally made in bacteria (E.coli, most commonly). These organisms do not have the ability to process the pre-mRNA into mRNA, therefore it is necessary to use cDNA and not the original DNA sequence.
Reply:DNA contains non translated regions like introns. Only exon part of DNA is transcribed into mature mRNA, and then this mature mRNA is translated into protein via ribosomes. Every microorganisms has relatively different mechanisms governing mature mRNA production from DNA. If you use original DNA, bacteria which you insert DNA to express insulin can not produce mature mRNA, it only can transcribe mRNA together with introns. Then if these introns are translated with exons, then you get a totally different protein from insulin.


İnsulin composed of aminoacids, and each aminoacid is coded by codons in mRNA,simplest way to get insulin is to use mRNA and then produce complementary DNA from this mRNA to put into a plasmid(plasmid is kind of DNA, you can put cDNA into it), then transform into a host bacteria or yeast.