Molecular Basis of Inheritance Class 12 One Shot | NCERT Biology Chapter 5 | Board Exam 2027

Raat ke 2 baje, crime scene. Na koi witness, na CCTV, na fingerprint… bas ek single baal 🔍 Aur usi ek baal se culprit pakda gaya. Kaise? Jawab hai DNA! Is video mein poora chapter "Molecular Basis of Inheritance" (Class 12 Biology, NCERT Chapter 5) ek hi video mein, Netflix-thriller style: DNA structure aur double helix, packaging (nucleosome), Griffith, Avery aur Hershey-Chase, DNA vs RNA, RNA world, Meselson-Stahl aur replication, transcription, genetic code, mutation aur tRNA, translation, lac operon, Human Genome Project, aur end mein DNA fingerprinting se crime ka reveal. Saath mein 10 board exam ke most-asked questions solved + 10-question rapid quiz. Short notes neeche hain, full PDF notes ka link bhi 👇 CHAPTERS 0:00 Cold open: crime scene aur ek baal 1:08 Intro 2:07 DNA kya hai? 3:44 Nucleotide: DNA ke building blocks 6:07 Double helix: Watson & Crick 8:32 Central dogma 9:21 DNA packaging: 2.2 metre ka jugaad 12:07 Griffith: transforming principle 14:06 Avery, MacLeod & McCarty 15:22 Hershey-Chase: blender experiment 17:13 DNA vs RNA + RNA world 19:55 Replication: semiconservative, Meselson-Stahl 22:37 Replication machinery: fork, polymerase, ligase 25:09 Transcription: template vs coding strand 27:32 Gene, exons-introns & types of RNA 29:46 Eukaryotic transcription: Pol I/II/III, splicing, capping, tailing 31:33 Genetic code: 64 codons & features 34:16 Mutation (frameshift) & tRNA adapter 36:52 Translation: ribosome factory 39:20 Gene regulation & lac operon 42:59 Human Genome Project 46:58 DNA fingerprinting: case solved! 50:33 Board exam ke most-asked questions 54:36 Rapid quiz: 10 questions 57:40 Outro 📖 KEY NOTES | MOLECULAR BASIS OF INHERITANCE • DNA is a polymer of deoxyribonucleotides. φ×174: 5386 nucleotides; E. coli: 4.6 × 10⁶ bp; haploid human DNA: 3.3 × 10⁹ bp. • Nucleotide = Base + Sugar + Phosphate. Purines: A, G. Pyrimidines: C, T, U. DNA nucleotides are joined by 3′–5′ phosphodiester bonds. • DNA double helix (Watson & Crick, 1953): Antiparallel, right-handed. A=T (2 H-bonds), G≡C (3 H-bonds). One turn = 3.4 nm, 10 bp; distance between bp = 0.34 nm. • Central Dogma: DNA → RNA → Protein. Some viruses show reverse transcription (RNA → DNA). • DNA Packaging: Histones form octamers; DNA wraps around them to form nucleosomes. Euchromatin is loosely packed and active; heterochromatin is densely packed and generally inactive. • Griffith Experiment (1928): Heat-killed S + live R bacteria caused mice to die, demonstrating transformation. • Avery, MacLeod & McCarty: DNase stopped transformation, proving DNA is hereditary material. • Hershey-Chase Experiment (1952): ³²P-labelled DNA and ³⁵S-labelled protein confirmed DNA as genetic material. • Meselson-Stahl Experiment (1958): ¹⁵N and ¹⁴N density gradient experiment proved semiconservative replication. • DNA Replication: DNA polymerase works 5′ → 3′. Leading strand is continuous; lagging strand is discontinuous. DNA ligase joins Okazaki fragments. Eukaryotic replication occurs during S-phase. • Transcription: DNA → RNA. Transcription unit includes promoter, structural gene and terminator. Template strand: 3′ → 5′; coding strand: 5′ → 3′. • RNA Processing: Exons remain in mature RNA; introns are removed. Eukaryotic RNA polymerases I, II and III synthesise different RNA types. • Genetic Code: 64 codons; 61 sense and 3 stop (UAA, UAG, UGA). AUG codes for methionine and acts as initiator codon. • Mutation: Sickle-cell anaemia is caused by a point mutation in β-globin, changing glutamic acid to valine. Insertions/deletions may cause frameshift mutations. • tRNA: Adapter molecule with anticodon loop and amino acid acceptor end. Secondary structure is cloverleaf-shaped. • Translation: Protein synthesis from mRNA. Amino acids attach to tRNA using ATP. Ribosomes contain rRNA and proteins; release factors recognise stop codons. • Lac Operon (Jacob & Monod): i gene forms repressor; z gene forms β-galactosidase; y forms permease; a forms transacetylase. Lactose/allolactose acts as inducer. • Human Genome Project (1990–2003): Sequenced human genome, approximately 3.2 billion bp. Less than 2% codes for proteins; about 99.9% DNA is common among humans. • DNA Fingerprinting (Alec Jeffreys): Based on VNTR polymorphism. Steps: DNA isolation → restriction digestion → electrophoresis → blotting → hybridisation → autoradiography. Uses: forensic identification, paternity testing and genetic diversity. 📄 Full PDF notes: [https://drive.google.com/file/d/1612I...] #Class12Biology #MolecularBasisOfInheritance #NCERTBiology #DNA #DNAFingerprinting #LacOperon #HumanGenomeProject #NEET #CBSE #BoardExam #OneShot #SimpleLearningHub