Question

Can you find out why the distance between two polynucleotide chains in DNA remains almost constant?

Answer 1

Part 1: Introduction to double helical structure of DNA

• Double helix structure of DNA consists of two polynucleotide chains in DNA.
• Both these chains are arranged in an antiparallel manner and are complementary to each other.
• One chain has polarity 3’--> 5’ and the other chain has polarity 5’--> 3’.
• Both these chains are aligned together with hydrogen bonds between nitrogenous bases.

Part 2: Reason for constant distance between polynucleotide chains

1. The distance between two polynucleotide chains in DNA remains almost constant because : The hydrogen bonds between purines and pyrimidines are hydrophobic in nature and resist any change in the distance between the 2 polynucleotide chains.
2. The pairing of a purine base with a pyrimidine base creates approximately uniform distance between the two strands of DNA helix.