Base Pairing And Hydrogen Bonds: Key To DNA Stability

Base Pairing And Hydrogen Bonds: Key To DNA Stability

Question 1. Watson and Crick’s model of DNA structure
Answer:

Double Helical Structure of DNA:

• Proposed by James Watson and Francis Crick in 1953

Features:

• It is a right-handed double helix
• Consists of two polydeoxyribonucleotide chains twisted around each other
• The bases present are adenine
• (A), Guanine(G), Cylosine(C) and Thymine(T)
• Two strands are antiparallel, one running from 5′ to 3′ and the other vice versa Width is 20 A°
• Each turn of helix is 34 A° with 10 pairs of nucleotides
  Two strands are held together by hydrogen bonds
• The A-T pair has 2 hydrogen bonds, G-C pair has 3 hydrogen bonds
  Content of adenine equals thymine and guanine equals cytosine – Char gaff’s rule

Question 2. What are nucleosides & nucleotides? Give examples of each
Answer:

Nucleotide:

• They are composed of a nitrogenous base, a pentose sugar & a phosphate
• They are monomeric units in the nucleic acid

Nucleoside:

• Nucleoside is a nucleotide without esterified phosphate groups
• Examples

Question 3. Name different types of RNA & their functions
Answer: