Which best describes how scientists found the human gene that makes insulin?

Scientists worked  backwards by looking into the amino acid sequence to determine the DNA base. They started with the mRNA which transcribes the codon into respective amino acids. This human gene is found on top of chromosome 11 in human DNA.
Hope this helps!

They took the DNA from the pancreas till they found the Gene that coded for insulin and either used bacteria or i think its called PFR or PRF to create copious amounts for people