NEET · Subject-wise preparation

Genetics and evolution for NEET: concepts, problems and traps

By the PrepMatic team · Updated 8 Oct 2026 · 7 min read

Genetics and Evolution is unit 7 of the NMC's 10 Biology units, and it is the one Biology unit that mixes recall with calculation: crosses, ratios, pedigrees, a base-sequence question, and a Hardy-Weinberg sum. Learn it in four blocks: the principles of inheritance, the chromosomal basis and sex determination, the molecular basis (DNA to RNA to protein), and evolution. This page owns the depth; the overall Biology approach is in NEET Biology preparation.

What the unit covers

The NMC lists Genetics and Evolution as a single unit. The breakdown below follows the usual NCERT chapters, which is our mapping.

For how often the unit is asked relative to others, see NEET high weightage chapters.

Mendelian ratios you must know cold

The classic trap is incomplete dominance and codominance, where the phenotype ratio is the same as the genotype ratio. In codominance, such as the I^A and I^B alleles of the ABO blood group, both alleles are fully expressed in the heterozygote, which is why I^A I^B gives blood group AB.

Worked problems

Product rule. For RrYy × RrYy, the chance of a wrinkled, green (rryy) offspring is the chance of rr times the chance of yy: 1/4 × 1/4 = 1/16. The chance of round and yellow is 3/4 × 3/4 = 9/16. Multiplying single-gene probabilities is faster than drawing a 16-box square.

Blood groups. A parent of genotype I^A i and another of genotype I^B i can have children of groups AB, A, B and O, each with probability 1/4.

X-linked inheritance. A carrier mother (X^H X^h) and a normal father (X^H Y) give four equally likely children: a normal daughter, a carrier daughter, a normal son and a haemophilic son. So half the sons are affected, and no daughter is affected.

Hardy-Weinberg. If 16% of a population shows a recessive trait, then q² = 0.16, so q = 0.4 and p = 0.6. Carriers are 2pq = 2 × 0.6 × 0.4 = 0.48, or 48%. Check: 0.36 + 0.48 + 0.16 = 1.

Reading pedigrees

• Two unaffected parents with an affected child point to a recessive trait.
• If every affected person has an affected parent, suspect a dominant trait.
• A trait that skips generations and affects mainly males suggests X-linked recessive. An affected father cannot pass an X-linked trait to a son.
• Decide dominant or recessive first, then autosomal or X-linked, and test the answer on every family in the chart.

Sex determination and linkage

• Humans: XX female, XY male, so the male is heterogametic.
• Birds: ZW female, ZZ male, so the female is heterogametic.
• Grasshopper: XX female, XO male.
• Honey bee: haplodiploid. Drones develop from unfertilised eggs and are haploid; queens and workers are diploid.

Linked genes on the same chromosome do not assort independently. The closer two genes are, the fewer the recombinants, and one percent recombination equals one map unit. Morgan's work on Drosophila is the standard example.

Genetic disorders

Molecular basis: experiments and numbers

Chargaff's rule is A = T and G = C. In B-DNA there are 10 base pairs per turn, a pitch of 3.4 nm, and 0.34 nm between adjacent base pairs.

The genetic code

The code is triplet and degenerate, and it is nearly universal. There are 64 codons: 61 code for amino acids and three (UAA, UAG, UGA) are stop codons. AUG codes for methionine and is the start codon.

Worked problem. A template strand reads 3′-TACGGA-5′. The mRNA is built antiparallel and complementary: 5′-AUGCCU-3′. Reading codons gives AUG (methionine) and CCU (proline). Always work out which strand is the template before transcribing, since the coding strand has the same sequence as the mRNA, with T replaced by U.

Operon and genome

In the lac operon, the i gene codes for a repressor. Without lactose the repressor binds the operator and blocks transcription. Lactose, the inducer, binds the repressor and the structural genes lacZ, lacY and lacA are transcribed. The Human Genome Project established that the human genome has about 3 × 10⁹ base pairs. DNA fingerprinting uses variable number tandem repeats (VNTRs).

Evolution

Mistakes that cost marks

• Giving a genotype ratio when the question asks for the phenotype ratio, or the reverse.
• Writing gametes wrongly: from AaBb they are AB, Ab, aB and ab, not Aa and Bb.
• Mixing up the template and coding strands, or forgetting that mRNA is antiparallel to the template.
• Applying Hardy-Weinberg without its assumptions: a large population, random mating, and no mutation, migration or selection.
• Confusing chromosome numbers in Down, Turner and Klinefelter syndromes.
• Attributing an experiment to the wrong scientist or the wrong conclusion.

How to practise

Solve every cross twice, once with a Punnett square and once with the product rule, and see if both agree. Do ten mixed problems a week: two crosses, one pedigree, one Hardy-Weinberg sum, one base-sequence question and five recall questions. Keep one-page sheets for the experiments, the disorders and the evolution terms and revise them on the cycle in the NEET revision strategy. Check against real questions with the method in NEET previous year question papers, and read the NCERT chapters line by line using NCERT for NEET.

Using PrepMatic for genetics

PrepMatic's free assessment of about 15 untimed questions shows whether Biology is a weak subject for you, at subject level rather than chapter level. When genetics comes up in your Roadmap, you can check it with a topic test of about 15 questions in 30 minutes, and you can upload your own one-page sheets to generate a mock from them. Full-length mocks that match the paper show how your Biology accuracy holds up under time pressure.

Frequently asked questions

Is genetics important for NEET?

Yes. Genetics and Evolution is a full NMC unit and mixes recall with calculation. Exactly how many questions it gets varies from year to year, so see the tiers in high weightage chapters rather than a fixed count.

How do I solve genetics problems quickly?

Write the parent genotypes, list the gametes, and use the product rule for each gene separately, then multiply. Draw a Punnett square only when the question asks for a full ratio.

Is the lac operon in the NEET syllabus?

The NMC lists Genetics and Evolution as a unit and the lac operon is part of the usual NCERT chapter on the molecular basis of inheritance. Confirm the sub-topics in the NMC PDF.

Which scientists and experiments should I know?

Mendel, Morgan, Griffith, Avery-MacLeod-McCarty, Hershey-Chase, Meselson-Stahl, Chargaff and Watson-Crick for genetics, and Darwin, Lamarck, Oparin-Haldane and Miller-Urey for evolution. Match each to a one-line conclusion.

Are evolution questions mostly theory?

Largely. Evolution questions are usually recall or matching, with an occasional calculation such as a Hardy-Weinberg sum. Learn the definitions and examples exactly as NCERT states them.

Official sources

• National Medical Commission (NMC): the NEET-UG syllabus notified on 22 December 2025.
• NEET-UG official website (NTA): information bulletin, notices and answer keys.
• NCERT: free Class 12 Biology textbooks.

Confirm sub-topics in the latest NMC notification. For the full exam, return to the NEET guide.

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