Molecular Basis of Inheritance — Class 12 Maharashtra HSC Biology revision notes
A 7-page visual revision sheet for Molecular Basis of Inheritance, written for Class 12 Maharashtra HSC Biology. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.
Page 1 as PDF
Molecular Basis of Inheritance in one look
three experiments that proved DNA, then how it packs, copies, and gets read
Proving DNA Is the Genetic Material
- 1869: Miescher isolated a phosphorus-rich acidic substance from WBC nuclei, nucleic acid
- by the early 1900s: known as a mix of proteins, DNA and RNA
- proteins (complex, varied) were long favoured over DNA (thought simple) as genetic material
- that assumption held from roughly 1928 to 1952, then was overturned
Three Experiments, in Sequence
- Griffith (1928): live R + heat-killed S: mice died, live S recovered. dead S held a transforming principle
- Avery, MacLeod, McCarty (1944): only purified DNA transformed R into S. DNase blocked it, proteases and RNases did not: the principle IS DNA
- Hershey-Chase (1952): phage DNA (32P) entered E. coli, phage protein (35S) stayed outside: DNA carries heredity
Why DNA, Not RNA, Won as the Standard
- DNA is large, stable, chemically simple, stores vast information, replicates with fidelity
- retroviruses use RNA as sole genetic material, the exception that proves DNA is the cell rule
The Packaging Problem
- a mammalian cell's DNA stretches ≈2.2 m, the nucleus is only ~10^-6 m across
- prokaryotes (e.g. E. coli): no nuclear membrane; naked circular nucleoid, ~1560 μm, 4.6 million bp
- nucleoid coils into a ~500 μm circle, then 40-50 loops of ~30 μm, each supercoiled to ~2 μm
- HU proteins (positively charged) and DNA gyrase/topoisomerase I assist the coiling
Page 1 of 7. The full sheet, all 7 pages, opens free in the app.
What this Molecular Basis of Inheritance sheet covers
- Proving DNA Is the Genetic Material
- Three Experiments, in Sequence
- Griffith (1928)
- Avery, MacLeod, McCarty (1944)
- Hershey-Chase (1952)
- Why DNA, Not RNA, Won as the Standard
- The Packaging Problem
- Packaging in Eukaryotes: the Nucleosome
- Heterochromatin vs Euchromatin
- Heterochromatin
- Euchromatin
- DNA Replication, the Steps
- Meselson and Stahl (1958): Proving Semiconservative
- DNA's Two Functions
- Transcription: DNA to mRNA
- hnRNA Processing in Eukaryotes
- The Genetic Code
- Eight Characteristics of the Code
- Triplet
- Has polarity
- Non-overlapping
- Commaless
- Degenerate
- Universal
- Non-ambiguous
- Start / stop
- Mutation and the Reading Frame
- tRNA: the Adapter Molecule
- Translation, Three Stages
- Initiation
- Elongation
- Termination
- Regulation of Gene Expression, and the Operon
- Lac Operon, Component by Component
- Switching the Operon On
- Genomics and the Human Genome Project
- Genome Sizes, Compared
- DNA Fingerprinting
- DNA Fingerprinting, Step by Step
- Isolation + digestion
- Electrophoresis + blotting
- Probe hybridisation
- Where It's Used
- Forensics
- Parentage disputes
- Pedigree analysis
- Terms Worth Keeping Straight
- Traps that cost marks
- Tricks that save time
How CapCompass uses this sheet
These notes are not a standalone PDF. CapCompass plans Biology chapter by chapter against your real exam dates and free hours, and when the plan reaches Molecular Basis of Inheritance the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.
More Biology Class 12 revision notes
- Biodiversity, Conservation and Environmental Issues
- Biotechnology
- Control and Co-ordination
- Ecosystems and Energy Flow
- Enhancement of Food Production
- Human Health and Diseases
- Inheritance and Variation
- Organisms and Populations
- Origin and Evolution of Life
- Plant Growth and Mineral Nutrition
- Plant Water Relation
- Reproduction in Lower and Higher Animals
- Reproduction in Lower and Higher Plants
- Respiration and Circulation