Molecular Basis of Inheritance ; Class 12th + NEET Important questions

1. Introduction 

  • Molecular Basis of Inheritance explains how Genetic information is stored and transferred 
  • Main molecules: 
  • DNA
  • RNA
*DNA is the genetic material in most organisms 

2. DNA Structure (very important )


Digram : DNA Double Helix 

*Structure: 
  • Double Helix (Watson and crick ,1953 )
  • Two strands: Antiparallel 
  • Backbone : Sugar + phosphate 
  • Bases - A, T, G, C

*Base Pairing:
  • A = T (2 bonds)
  • G =- C (3 bonds)
Chargaff's rule: A=T, G=C

3. Packaging of DNA 


Digram : Nucleosome 

  • DNA wraps around histone proteins 
  • Forms nucleosome
  • Helps fit Long DNA inside nucleus 

4. Search for Genetic material 

  • Griffith Experiment: Transformation discovered 
  • Hershey and Chase: DNA = Genetic material 
Most ask Theory 

5. DNA replication 

Digram : DNA replication 

  • Key Points:
  1. Semiconservation
  2. Enzymes : 
  • DNA polymerase 
  • Helicase
  • Ligase
Leading vs lagging strand ( very important)

6. Transcription (2025 question)

Digram : Transcription 
DNA - mRNA
Enzyme - RNA polymerase 

RNA type : 
  • mRNA
  • tRNA
  • rRNA

7. Genetic Code 

Features:
  • Triplet code 
  • Universal 
  • Degenerate
*Example : AUG = start Codon

8. Translation 

Digram : Translation 

  • mRNA -- Protein 
  • Occurs in Ribosome
  • tRNA adapter molecule

9. Regulation Of Gene Expression 

Digram : lac operon

Works in bacteria 
Components:
  • Promoter
  • Operator
  • Structural genes
Lactose present --  Gene ON

10. Human Genome Project 

  • Study of Complete Human DNA
  • Genome = Total genes
  • Important fact base questions 

11. DNA Fingerprinting


Used in :
  • Crime detection
  • Paternity test

NEET Important Topics 

  1. DNA Structure (most Important)
  2. DNA replication 
  3. Transcription and translation 
  4. Genetic Code 
  5. Lac operon 
  6. DNA Fingerprinting 
  7. HGP
Direct NCERT lined based questions 

Most Expected questions 

Theory questions 

  1. Explain Watson and Crick model of DNA
  2. Describe DNA replication 
  3. What is Genetic Code
  4. Explain Lac operon
  5. Describe Transcription process

Diagram questions 

  1. DNA Double Helix 
  2. Replication Fork
  3. Transcription 
  4. Translation 
  5. Lac operon 
If you want more chapter notes 



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