Learning Objective - Struture Of DNA

Question 1

DNA (Nucleotide Composition)

Answer 1

Nucleotides - deoxyribose sugar, a phosphate group, 1/4 nitrogenous bases (A, T,G,C)
The sugar-phosphate backbone is linked by phosphodiester bonds

Question 2

Double Helix Structure

Answer 2

DNA forms a right-handed double helix with 2 antiparallel strands
A -> T (2 H bonds)
C-> G (3 H bonds)
Base stacking interactions (hydrophobic interactions) between adjacent bases

Question 3

Grooves + Functionality

Answer 3

Double helix creates major + minor grooves essential for protein-DNA interactions
Proteins (transcription factors) bind to these grooves to regulate gene expression

Question 4

Structural Variants

Answer 4

B-DNA
A-DNA - more compact + dehydrated form, with deeper grooves
Z-DNA - Left-handed helix, associated with gene regulation under certain conditions

Question 5

DNA Stability Factors

Answer 5

Phosphate backbone provides solubility + structural intergrity
Hydrogen bonding between base pairs + base stacking interactions ensure the double helix’s stability
Metal ions neutralise the negative charge of the phosphate backbone

Question 6

Impact of DNA - Alkylating Agents

Answer 6

Alkylating agents target DNA’s nucleophillic sites, causing structural changes that disrupt replication + transcription
E.g Cisplatin,