<prompt> DNA model described by Watson and Crick wasRight handed parallelLeft handed anti parallelRight handed anti parallelRight handed parallel  <response>: The DNA molecule consists of two polynucleotide chains or strands that spirally twisted around each other and coiled around a common axis to form a right-handed double-helix. The two strands are antiparallel i.e. they ran in opposite directions so that the 3 end of one chain facing the 5 end of the other. The sugar-phosphate backbones remain on the outside, while the core of the helix contains the purine and pyrimidine bases. Ref-Sathyanarayana 4e p400 