This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
The Watson's Crick double helix model of DNA is 
Select and explain. 
A. Right handed anti parallel, B. Left handed anti parallel, C. Right handed parallel, D. Left handed parallel
A: Right handed anti parallel
Answer: A: Right handed anti parallel 
Explanation: Ans. (a) Right handed anti parallelRef: Harper's Biochemistry, 30th edn. pg. 360-361* Helical structure assumed by two strands of deoxyribonucleic acid, held together throughout their length by hydrogen bonds between bases on opposite strands, referred to as Watson-Crick base pairing. The structure is right handed anti-parallel structure.