. Crick - 1953Double Helix Model of DNATwo sources of information:1. Base composition studies of Erwin Chargaff•indicated double-stranded DNA consists of ~50% purines (A,G) and ~50% pyrimidines. H. Crick - 1953Double Helix Model of DNATwo sources of information:2. X-ray diffraction studies - Rosalind Franklin & Maurice WilkinsConclusion-DNA is a helical structure with distinctive. varying numbers of chromosome of different sizes and morphologies -the karyotype (e.g., pea, 2N = 14; human, 2N = 46, fruit fly, 2N= 8). The Search for the Molecular Basis of Heredity The Search...