CBSE Class 12 Biology Important Topics 2027
Every topic ranked by how often and how recently it was asked in 5 board + 2 official sample papers (2022–2026). Blue = board paper, green = sample paper.
Top 10 most important topics
| # | Topic | Chapter | Asked in | Importance |
|---|---|---|---|---|
| 1 | Tools of recombinant DNA technology (restriction enzymes, vectors, host organism) | Biotechnology - Principles and Processes | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★★ |
| 2 | Processes of recombinant DNA technology (steps of gene cloning) | Biotechnology - Principles and Processes | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| 3 | Immunity: innate and acquired; vaccination and immunisation | Human Health and Disease | Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★★★☆ |
| 4 | DNA structure and the search for genetic material (Griffith, Hershey-Chase) | Molecular Basis of Inheritance | Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| 5 | Structure of flower; microsporogenesis and structure of pollen grain | Sexual Reproduction in Flowering Plants | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 6 | Pollination: types, agents and outbreeding devices | Sexual Reproduction in Flowering Plants | Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★★☆☆ |
| 7 | Darwinism, natural selection and the Hardy-Weinberg principle | Evolution | Board 2023Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 8 | Microbes in sewage treatment and biogas (energy) production | Microbes in Human Welfare | Board 2022Board 2023Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 9 | Transcription | Molecular Basis of Inheritance | Board 2023Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 10 | Common diseases in humans and their pathogens | Human Health and Disease | Board 2022Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
Chapter-wise important topics
Sexual Reproduction in Flowering Plants · Reproduction
| Structure of flower; microsporogenesis and structure of pollen grain asked 7× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Pollination: types, agents and outbreeding devices asked 7× | Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★★☆☆ |
| Apomixis, polyembryony, parthenocarpy and significance of seed/fruit asked 4× | Board 2024Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Double fertilisation; development of endosperm and embryo asked 4× | Board 2023Board 2025Sample 2026 | ★★☆☆☆ |
| Megasporogenesis and development of the embryo sac asked 1× | Board 2026 | ★☆☆☆☆ |
Human Reproduction · Reproduction
| Fertilisation, implantation and embryonic development / pregnancy asked 6× | Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Menstrual cycle asked 3× | Board 2025Board 2026Sample 2026 | ★☆☆☆☆ |
| Gametogenesis: spermatogenesis and oogenesis asked 2× | Board 2026Sample 2025 | ★☆☆☆☆ |
| Male and female reproductive systems asked 2× | Board 2023Board 2026 | ★☆☆☆☆ |
| Parturition and lactation asked 1× | Sample 2025 | ★☆☆☆☆ |
Reproductive Health · Reproduction
| Birth control methods and contraception asked 5× | Board 2023Board 2024Board 2025Sample 2026 | ★★☆☆☆ |
| Infertility and assisted reproductive technologies (IVF, ZIFT, GIFT) asked 5× | Board 2023Board 2024Board 2026Sample 2025 | ★★☆☆☆ |
| Medical termination of pregnancy (MTP) and amniocentesis asked 1× | Board 2025 | ★☆☆☆☆ |
Principles of Inheritance and Variation · Genetics and Evolution
| Mendel's laws of inheritance and monohybrid/dihybrid crosses asked 4× | Board 2026Sample 2026 | ★★☆☆☆ |
| Sex determination and pedigree analysis asked 5× | Board 2023Board 2026Sample 2025 | ★★☆☆☆ |
| Mendelian and chromosomal disorders (Down's, Turner's, Klinefelter's, haemophilia, colour blindness) asked 5× | Board 2024Board 2025Sample 2025 | ★★☆☆☆ |
| Chromosomal theory of inheritance; linkage and recombination asked 3× | Board 2023Board 2024Board 2025 | ★☆☆☆☆ |
| Incomplete dominance, co-dominance and multiple alleles (ABO blood groups) asked 2× | Board 2025 | ★☆☆☆☆ |
Molecular Basis of Inheritance · Genetics and Evolution
| DNA structure and the search for genetic material (Griffith, Hershey-Chase) asked 8× | Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| Transcription asked 6× | Board 2023Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Regulation of gene expression (lac operon); DNA fingerprinting; Human Genome Project asked 6× | Board 2023Board 2024Sample 2025Sample 2026 | ★★★☆☆ |
| Genetic code and translation asked 4× | Board 2024Board 2025Sample 2025Sample 2026 | ★★☆☆☆ |
| DNA replication asked 2× | Board 2023Sample 2025 | ★☆☆☆☆ |
Evolution · Genetics and Evolution
| Darwinism, natural selection and the Hardy-Weinberg principle asked 6× | Board 2023Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Adaptive radiation and mechanisms of evolution asked 2× | Sample 2025Sample 2026 | ★☆☆☆☆ |
| Origin of life and theories of evolution asked 3× | Board 2024Board 2026 | ★☆☆☆☆ |
| Evidences of evolution (homology, analogy, fossils) asked 2× | Board 2025Sample 2026 | ★☆☆☆☆ |
| Human evolution asked 2× | Board 2023Board 2025 | ★☆☆☆☆ |
Human Health and Disease · Biology and Human Welfare
| Immunity: innate and acquired; vaccination and immunisation asked 9× | Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★★★☆ |
| Common diseases in humans and their pathogens asked 7× | Board 2022Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Drugs and alcohol abuse asked 3× | Board 2025Board 2026Sample 2026 | ★☆☆☆☆ |
| AIDS and cancer asked 3× | Board 2023Board 2024Sample 2025 | ★☆☆☆☆ |
Microbes in Human Welfare · Biology and Human Welfare
| Microbes in sewage treatment and biogas (energy) production asked 7× | Board 2022Board 2023Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Microbes as biocontrol agents and biofertilisers asked 7× | Board 2022Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| Microbes in household and industrial products (antibiotics, fermented products) asked 2× | Board 2024Sample 2025 | ★☆☆☆☆ |
Biotechnology - Principles and Processes · Biotechnology and its Applications
| Tools of recombinant DNA technology (restriction enzymes, vectors, host organism) asked 14× | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★★ |
| Processes of recombinant DNA technology (steps of gene cloning) asked 10× | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★★☆ |
| Principles of biotechnology (genetic engineering and bioprocessing) asked 2× | Board 2023Sample 2026 | ★☆☆☆☆ |
Biotechnology and its Applications · Biotechnology and its Applications
| Transgenic animals and ethical issues (GEAC, biopiracy, patents) asked 7× | Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★★☆☆ |
| Applications in medicine (recombinant insulin, gene therapy, molecular diagnosis) asked 5× | Board 2023Board 2025Sample 2026 | ★★☆☆☆ |
| Applications in agriculture (Bt crops, pest-resistant plants, RNA interference) asked 5× | Board 2022Board 2024Board 2025Board 2026Sample 2025 | ★★☆☆☆ |
Organisms and Populations · Ecology and Environment
| Population interactions (mutualism, competition, predation, parasitism, commensalism) asked 4× | Board 2023Board 2026Sample 2025Sample 2026 | ★★☆☆☆ |
| Population attributes and growth models (exponential and logistic) asked 4× | Board 2022Board 2023Board 2025Sample 2026 | ★☆☆☆☆ |
Ecosystem · Ecology and Environment
| Ecological pyramids and nutrient cycling asked 4× | Board 2023Board 2024Board 2026Sample 2026 | ★★☆☆☆ |
| Decomposition and energy flow asked 3× | Board 2025Board 2026Sample 2025 | ★☆☆☆☆ |
| Ecosystem structure, components and productivity asked 3× | Board 2024Board 2025Board 2026 | ★☆☆☆☆ |
Biodiversity and Conservation · Ecology and Environment
| Loss of biodiversity and its causes asked 5× | Board 2022Board 2025Board 2026Sample 2025 | ★★☆☆☆ |
| Biodiversity: concept, patterns and importance asked 6× | Board 2022Board 2023Board 2024Board 2026 | ★★☆☆☆ |
| Conservation of biodiversity (in-situ and ex-situ) asked 1× | Board 2026 | ★☆☆☆☆ |
Importance = how often a topic was asked × how recent, with extra weight for the latest official sample paper.