Brownlee was attempting to set up an assay to detect point mutations in DNA by forming DNA-32P RNA heteroduplexes and subsequently detecting Watson-Crick mismatches with RNases. He was helped by Andy Choo at the host laboratory. Choo provided Brownlee with DNA of different individuals (experiment 3). Brownlee intended to probe for RFLPs in the factor IX gene, following up work of Peter Winship in Brownlee's lab in Oxford. Mismatches had been detected before in other genes (see experiment 4,…