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NEET · Biology — Genetics, Molecular Biology & Evolution · Tamil Nadu, India

Biology — Genetics, Molecular Biology & Evolution for the NEET Exam — Tamil Nadu candidates

8% of the NEET test plan. Mendelian genetics, chromosomal theory, molecular basis of inheritance (DNA replication, transcription, translation), and evolution — approximately 15% of NEET Biology. Calibrated for Tamil candidates.

For candidates aiming to clear this exam on the first attempt, the difference between Band 6 and Band 7+ — or "passing" and "comfortable margin" — usually comes down to fluency on a small number of high-leverage topics. Biology — Genetics, Molecular Biology & Evolution sits at roughly 8% of the National Eligibility cum Entrance Test content distribution — Genetics and Evolution (NCERT Class 12 Units 5 and 7) is one of the highest-weightage Biology topics in NEET. It is also the topic that rewards careful NCERT reading most directly — cross-problems (monohybrid, dihybrid) follow predictable Punnett square logic, and molecular biology questions are NCERT-definition based. Evolution questions (Darwin's theory, Hardy-Weinberg, speciation) are purely conceptual. Pass rates for the NEET are published annually by the awarding body and vary by cohort and locale. For Tamil Nadu candidates preparing for NEET, the calibration of study to local context matters: Tamil Nadu uses 7.5% NEET government-school reservation and runs separate state-quota counselling. JEE Main and GATE candidate volumes are second only to Maharashtra.

Pass rates for NEET (Tamil Nadu, India) are published periodically by the awarding body.

Common failure modes

These are the patterns that cause most candidates to lose marks on this topic. Recognising them in advance is half the work.

  • !Punnett square errors in dihybrid crosses — forgetting to apply independent assortment (9:3:3:1 ratio for two independent traits)
  • !Confusing co-dominance (both alleles expressed, e.g., AB blood type) with incomplete dominance (blended phenotype, e.g., pink snapdragons)
  • !Misidentifying the steps of DNA replication vs transcription (which enzyme makes what)
  • !Forgetting Hardy-Weinberg equilibrium conditions — mutation, selection, gene flow, non-random mating, and genetic drift ALL violate the equilibrium
  • !Confusing convergent evolution (analogous organs, unrelated species) with divergent evolution (homologous organs, common ancestry)

Study tips

  • 1Practise Punnett squares for monohybrid (3:1 ratio), dihybrid (9:3:3:1), and test cross scenarios. NEET tests all three.
  • 2For molecular biology, memorise the central dogma: DNA → (transcription) → mRNA → (translation) → Protein. Know the enzyme: DNA polymerase (replication), RNA polymerase (transcription), ribosome (translation).
  • 3Learn the genetic code features from NCERT: it is universal, degenerate (multiple codons per amino acid), non-overlapping, and unambiguous. AUG is start (methionine), UAA/UAG/UGA are stop codons.
  • 4Memorise Hardy-Weinberg equation: p² + 2pq + q² = 1 (genotype frequencies) and p + q = 1 (allele frequencies). NEET uses these directly in numerical questions.
  • 5For evolution, know the evidence types: comparative anatomy (homologous vs analogous structures), embryology, fossil record, molecular biology. Darwin's natural selection vs Lamarck's inheritance of acquired characteristics.
  • 6NEET-UG is offered in Tamil (தமிழ்) at all TN centres. Many state-board students prefer Tamil-medium for biology questions but English-medium for physics and chemistry — you must choose one medium for the entire paper.
  • 7For TN MBBS admission: register on TN Health website for the 7.5% government-school reservation if eligible — separate from MCC counselling.
  • 8GATE Chennai and Coimbatore centres fill fastest; submit your GATE application within 72 hours of opening to secure your preferred centre.

Sample NEET Biology — Genetics, Molecular Biology & Evolution questions

These sample items mirror the format and difficulty of real NEET questions. Practice with thousands more on the free Koydo question bank.

  1. 1

    In a monohybrid cross between two heterozygous parents (Tt × Tt), the expected phenotypic ratio is:

    • A1:2:1
    • B3:1Correct
    • C1:1
    • D2:1
    Why this answer?

    Cross Tt × Tt → TT : 2Tt : tt = 1:2:1 genotypic ratio. If T is dominant over t, then TT and Tt both show the dominant phenotype. Phenotypic ratio = 3 dominant : 1 recessive = 3:1.

  2. 2

    The enzyme responsible for DNA replication is:

    • ARNA polymerase
    • BDNA ligase only
    • CDNA polymerase IIICorrect
    • DHelicase only
    Why this answer?

    DNA polymerase III (in prokaryotes) is the primary enzyme that synthesises new DNA strands by adding nucleotides complementary to the template strand. Helicase unwinds the double helix; DNA ligase joins Okazaki fragments; RNA polymerase makes RNA, not DNA.

  3. 3

    Homologous organs are evidence for:

    • AConvergent evolution
    • BDivergent evolution (common ancestry)Correct
    • CParallel evolution
    • DCo-evolution
    Why this answer?

    Homologous organs have the same basic structural plan and evolutionary origin but may perform different functions (e.g., forelimbs of humans, whales, bats, horses). They indicate divergent evolution — common ancestry with adaptation to different environments. Analogous organs (wings of insects vs birds) indicate convergent evolution from different ancestry.

Frequently asked questions

How many Genetics and Molecular Biology questions appear in NEET?
Genetics (Principles of Inheritance — Class 12 Chapter 5) and Molecular Basis of Inheritance (Chapter 6) together contribute approximately 8–12 NEET Biology questions. Evolution (Chapter 7) contributes another 3–5 questions. Combined, the unit accounts for roughly 15% of total NEET Biology marks.
Is human genetics (blood group inheritance, sex-linked disorders) tested in NEET?
Yes. Human genetics questions include ABO blood group inheritance, Rh factor, sex-determination (XX/XY), and sex-linked disorders (haemophilia, colour blindness — X-linked recessive). These are covered in NCERT Class 12 Chapter 5 and appear in almost every NEET paper.
What is the NEET pass rate for Tamil candidates?
Pass rates for NEET candidates in Tamil Nadu, India are published periodically by the awarding body. Practice questions, full-length simulations, and weak-area drills are the highest-impact way to improve your odds.
How long should Tamil candidates study Biology — Genetics, Molecular Biology & Evolution for the NEET?
For most candidates, focused mastery of Biology — Genetics, Molecular Biology & Evolution requires 20–40 hours of deliberate practice — drilling sample questions, reviewing failure modes, and timing yourself against exam conditions. Tamil Nadu uses 7.5% NEET government-school reservation and runs separate state-quota counselling. JEE Main and GATE candidate volumes are second only to Maharashtra. Combine Biology — Genetics, Molecular Biology & Evolution study with full-length mock exams in the final two weeks before your test date.

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Related study guides

Regulatory citation: NTA NEET-UG Information Bulletin — Biology syllabus: Genetics and Evolution (Class 12 Unit 5: Chapters 5–7).