I was learning today about genetic engineering specifically related to insulin production. I wanted to know how scientists initially found the right mRNA sequence that was related to the DNA sequence for insulin production?

This is a good place to start your research:
http://www.diabetes.co.uk/insulin/histo … sulin.html

From a quick look at Reetika's link I don't think it says how the DNA sequence for insulin was determined. In the very 'early' days of recombinant DNA technology fairly standard procedures were used. I think you will find that in the late 1970's scientists would have found the 'right' DNA sequence corresponding to the mRNA sequence for insulin! e.g., they cloned the cDNA for the insulin precursor mRNA.

I haven't searched for the papers (there will be extensive references to these on Google) to check the methods used but the basic idea would have been this: you knew the protein sequence for insulin (determined by Sanger in the 1950's), so make a DNA probe or probes corresponding to that protein sequence and use these probes to screen either a cDNA (constructed from mRNA) or genomic DNA library expressed in bacteria; then isolate bacterial clones that bind the probe(s) and sequence their cDNA or genomic DNA inserts. In that way you would find clones that have the DNA sequence corresponding to the probes you used in the first place, and expand them so that you would have millions of bacteria that would express the insulin cDNA or gene (that would be transcribed into insulin mRNA and translated into insulin protein). I think the DNA (hence mRNA) sequence for insulin was first obtained for rat, followed soon thereafter by human. Hope that helps!

Last edited by Steve Lolait (17th Mar 2016 09:48:08)