We were trying to identify a fragment of DNA corresponding to a human insulin gene, it's actually a DNA copy of an insulin RNA, and we have a human insulin of a tumor, human tumor that makes insulin, which we thought we could take the RNA from, make a copy, identify a piece that would actually be the human insulin sequence. We could identify that by interacting that piece with a fragment of the rat insulin gene, which we already knew and use that as a tag, because the two genes have very, very similar sequences. We went through all the procedure, we run the material on what's called gel electrophoresis, moving up to a jelly-like material between glass plates, and we found what we thought was the human insulin gene. When we got back home we discovered that what we had actually isolated was the same rat insulin gene we had started with, that the gel plates we had brought, the glass plates, were contaminated with rat insulin from earlier experiments done here that had, we had actually by these very, very sensitive techniques been able to re-isolate essentially contaminant, the contaminating material rather than the material we wanted to find.

human insulin gene,rat insulin,porton down,gene walter,dna copy,gel electrophoresis,walter gilbert,recombinant dna,sensitive techniques,dnai,glass plates,human tumor,interviewee,rna,moratorium,fragment,genes,sequences,manipulation,england