NEET Biology · Genetics PYQ
NEET Genetics Previous Year Questions (2005–2025)
Genetics is among the highest-yield blocks in NEET Biology — Principles of Inheritance plus Molecular Basis of Inheritance together carry roughly ~11% of Biology marks on trend, often 4–5 questions per NEET paper. Strong rankers treat this block as near-non-negotiable.
Genetics PYQs spanning AIPMT 2005 to NEET 2025, covering Mendelian inheritance, chromosomal theory, linkage, DNA structure and replication, transcription, translation and the genetic code. Every question links to the specific NCERT Class 12 line it's derived from.
Genetics (Principles of Inheritance + Molecular Basis) at a Glance
Key Sub-Topics & What's Tested
Mendel's Laws of Inheritance
Law of dominance, segregation, independent assortment. Monohybrid and dihybrid cross ratios, test cross, back cross.
Beyond Mendel
Incomplete dominance (4 o'clock plant), codominance (blood groups), multiple alleles (ABO blood typing), polygenic inheritance, pleiotropy.
Chromosomal Theory & Linkage
Sutton-Boveri chromosomal theory, linkage & recombination, Morgan's Drosophila experiments, crossing over.
Sex Determination & Sex Linkage
XX-XY, XX-XO, ZW-ZZ systems, human sex determination, haemophilia, colour blindness pedigree analysis.
Mutations & Genetic Disorders
Chromosomal disorders (Down, Klinefelter, Turner syndromes), Mendelian disorders (sickle cell, thalassemia, PKU, haemophilia), gene mutations.
DNA Structure & Packaging
Watson-Crick double helix, Chargaff's rules, nucleosome structure, euchromatin vs heterochromatin, histones H1 to H5.
DNA Replication
Semiconservative replication (Meselson-Stahl), replication fork, leading vs lagging strand, Okazaki fragments, DNA polymerases.
Transcription & Translation
mRNA synthesis, initiation/elongation/termination, codon table, wobble hypothesis, tRNA structure, ribosome assembly.
Gene Expression Regulation
Operon concept (Lac operon in detail), inducer/repressor/operator, positive and negative regulation.
Human Genome Project
Goals, methodology, results (total genes, chromosome size, repeat sequences), applications and ethical implications.
Question Type Distribution
| Question Type | Share (approx) | Example Pattern |
|---|---|---|
| Cross Ratios & Phenotype Counting | 20% | Find phenotypic ratio in F2 of a dihybrid cross with one incompletely dominant gene. |
| Pedigree Analysis | 10% | Given a pedigree, determine mode of inheritance (autosomal dominant/recessive, X-linked). |
| NCERT-Line Recall (factual) | 30% | Which amino acid does the codon UAG represent? (Answer: stop codon) |
| Experiment Identification | 10% | Whose experiment demonstrated semiconservative DNA replication? (Meselson-Stahl) |
| Molecular Mechanism | 20% | Which enzyme joins Okazaki fragments? (DNA ligase) |
| Lac Operon & Gene Regulation | 10% | Match each Lac operon component (i, o, z, y, a) to its function. |
How to Solve Genetics (Principles of Inheritance + Molecular Basis) PYQs
- 1Read NCERT Class 12 Ch 5 and Ch 6 three times. Genetics PYQs are NCERT-line-level. Three passes lock in the recall patterns NTA tests.
- 2Practise cross ratios by drawing Punnett squares. Don't rely on formula memorisation for ratios — physically draw the 4x4 for dihybrid crosses.
- 3Memorise the codon table's special codons. Start (AUG = Met), Stop (UAA, UAG, UGA). These appear in every Genetics paper at least once.
- 4Learn experiments + scientists + year. Watson-Crick (1953), Meselson-Stahl (1958), Hershey-Chase (1952), Griffith (1928). NCERT asks direct “which scientist did X?” questions.
- 5Lac operon: know all 5 parts. Regulator (i), Promoter (p), Operator (o), Structural genes (z = β-galactosidase, y = permease, a = transacetylase). Lac operon questions appear in most NEET papers in some form — a perennial high-frequency topic.
- 6For pedigree, identify key features. Autosomal dominant = every affected person has affected parent. X-linked recessive = skips generations via female carriers. Train these patterns from PYQs.
Common Mistakes That Cost Marks
- Confusing incomplete dominance with codominance. Incomplete = intermediate phenotype (pink from red × white). Codominance = both alleles expressed (AB blood type from A × B).
- Wrong direction of replication. DNA synthesis is always 5' to 3'. Leading strand is continuous; lagging strand is synthesised in Okazaki fragments — also 5' to 3'.
- Miscounting chromosome numbers. Humans = 46 chromosomes (23 pairs). Gametes = 23. Down syndrome = 47 (trisomy 21). Know these numbers without thinking.
- Wrong Lac operon logic. Lac operon is inducible — OFF by default, ON when lactose present. Don't confuse with tryptophan operon (repressible).
- Using DNA rules for RNA. RNA replaces T with U. Thymine is DNA-specific. Uracil is RNA-specific. Watch the molecule carefully in the question.
Related NEET Practice
Frequently asked questions
How many Genetics PYQs should a serious NEET aspirant solve?
Target 150+ Genetics PYQs (Principles + Molecular combined) across AIPMT 2005 to NEET 2025. Given the ~11% weightage, this is the single most rank-impactful block in NEET Biology.
Is NCERT enough for Genetics NEET PYQs?
Yes — NCERT Class 12 Ch 5 (Principles of Inheritance) and Ch 6 (Molecular Basis of Inheritance), read 3+ times with chapter PYQs, is sufficient for 35+/40 in this block. NEET rewards NCERT fidelity over coaching summaries.
Are Genetics NEET PYQs calculation-heavy?
No — NEET Genetics is recall-heavy (NCERT facts, experiment identification, cross ratios). Calculation is limited to simple Punnett square outcomes and occasional pedigree probability. Much easier than JEE-level problem solving.
What's the highest-repeat Genetics PYQ topic?
Lac operon — appears in most NEET papers in some form, a perennial high-frequency topic. Component identification, regulatory logic, role of each gene. Master it fully — it's a free 4 marks most years.
Do I need to memorise the full codon table?
Not the full 64-codon table. Memorise start (AUG), stop (UAA, UAG, UGA) and the most-tested common codons (UUU/UUC = Phe, GGU/GGC/GGA/GGG = Gly). NCERT reads are enough for the rest.
How do pedigree PYQs typically appear?
Usually a given pedigree diagram, and you identify inheritance mode. Patterns to recognise: affected offspring from two unaffected parents = recessive; skipping generations = X-linked recessive; both sexes equally affected = autosomal; majority affected = dominant.
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