Seymour Benzer used phage T4 mutants, Experimental evidence that a gene is a linear sequence of nucleotide pairs. Some regions of chromosomes have "hot spots" for mutations. Benzer's experimental approach to fine structure mapping of the rII locus. Generated 1612 spontaneous point mutations and several deletions in rII locus identified two complementation groups, rIIA and rIIB. Mapped locations of deletions relative to each other using recombination. Mapped locations of point mutations relative to the deletions. Tested for recombination between all point mutations within the same complementation group.
