Scale: 30x106:1. Section of B-DNA double helix is based on data gained from X-ray diffraction studies. Clockwise double helix has 10.5 base pairs per coil, equivalent to a passage height of about 3.4 nm. Structure correlates closely with the model of DNA developed by Watson and Crick in 1953. In 1 piece; mounted on a rotating stand with green base. Size, 7 x 7 x 16-1/2" H.