DNA Double Helix Structure Features — NEET Biology
📚 Practice ConceptThe salient features of the Double-helix structure of DNA are as follows:
Which of the following statements are correct regarding the structural features of the DNA double helix that contribute to its stability and overall architecture? S1: The two polynucleotide chains in a DNA molecule are coiled in a left-handed fashion. S2: Hydrogen bonds between complementary base pairs are crucial, with Adenine forming three H-bonds with Thymine and Guanine forming two H-bonds with Cytosine. S3: The backbone of the DNA double helix is formed by alternating sugar and phosphate groups, with the nitrogenous bases projecting inwards. S4: Stacking interactions between successive base pairs in the double helix, in addition to hydrogen bonds, confer significant stability. S5: The anti-parallel polarity of the two DNA strands means that if one strand has a 5'→3' orientation, the other has a 3'→5' orientation.
View solution & NCERT explanation
Correct answer: D — S3, S4 and S5 are correct
The core concept revolves around the defining structural features of the DNA double helix and the forces that maintain its stability. S1: This statement is not correct. The NCERT states that 'The two chains are coiled in a right-handed fashion,' not left-handed. S2: This statement is not correct. Adenine forms 'two hydrogen bonds with Thymine' and Guanine forms 'three H-bonds' with Cytosine. The numbers are reversed in the statement. S3: This statement is correct. The backbone is constituted by sugar-phosphate, and bases project inside. S4: This statement is correct. Stacking of base pairs, along with H-bonds, provides stability to the helical structure. S5: This statement is correct. The anti-parallel polarity is a key feature of the DNA double helix. Therefore, statements S3, S4, and S5 are correct. Options A, B, and C contain incorrect statements S1 or S2 or both. The correct option is D as it correctly identifies the true statements about the DNA double helix structure.
What does NCERT say about salient features Double-helix structure?
Has this concept appeared in NEET?
Which chapter is this from?
Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.