This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
DNA model described by Watson and Crick was 
Select and explain. 
A. Right handed parallel, B. Left handed anti parallel, C. Right handed anti parallel, D. Right handed parallel
C: Right handed anti parallel
Answer: C: Right handed anti parallel 
Explanation: 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 4/e p400