Genetics and Evolution for NEET: how to revise it

Genetics and Evolution is one of the heaviest NEET Biology units. Here is what to revise in each chapter, and how to practise genetics problems.

Paper Predict Notes · 20 Jan 2026

Genetics and Evolution is consistently one of the heaviest units in NEET Biology. It combines memory, such as genetic disorders and the steps of transcription, with reasoning, such as working out ratios and pedigrees. Both kinds of question are very learnable.

Principles of Inheritance and Variation

Mendelian ratios

• Monohybrid cross (F2): phenotypic ratio 3:1, genotypic ratio 1:2:1.
• Dihybrid cross (F2): phenotypic ratio 9:3:3:1.
• Test cross: crossing with a recessive parent. A monohybrid test cross gives 1:1.

Beyond Mendel

• Incomplete dominance: flower colour in snapdragon, where the F2 phenotypic ratio is 1:2:1.
• Co-dominance and multiple alleles: ABO blood groups, where Iᴬ and Iᴮ are co-dominant and i is recessive.
• Linkage and recombination: genes close together on a chromosome tend to be inherited together.
• Polygenic inheritance: traits like human skin colour.
• Pleiotropy: one gene affecting several traits, as in phenylketonuria.

Sex determination

• XX-XY: humans and Drosophila, where the male is heterogametic.
• XX-XO: grasshopper.
• ZW-ZZ: birds, where the female is heterogametic.

Genetic disorders

• Mendelian disorders: Haemophilia and colour blindness: X-linked recessive. Sickle cell anaemia, phenylketonuria and thalassemia: autosomal recessive. Myotonic dystrophy: autosomal dominant.
• Chromosomal disorders: Down syndrome: trisomy of chromosome 21. Klinefelter syndrome: XXY. Turner syndrome: XO.

Make one table of disorder, type and inheritance pattern. It is one of the most repeated question sources in the unit.

Pedigree analysis

Learn the standard symbols and practise identifying whether a trait is dominant or recessive, and autosomal or X-linked, from a pedigree.

Molecular Basis of Inheritance

• DNA structure: double helix, base pairing, and Chargaff's rules.
• Search for genetic material: Griffith, Avery-MacLeod-McCarty and Hershey-Chase experiments.
• Replication: semi-conservative, shown by Meselson and Stahl; the roles of DNA polymerase and ligase; leading and lagging strands.
• Transcription: template and coding strands; processing of hnRNA in eukaryotes (splicing, capping and tailing).
• Genetic code: triplet, degenerate, universal; start codon AUG and three stop codons.
• Translation: the roles of mRNA, tRNA and ribosomes.

The lac operon

• i gene: codes for the repressor.
• z gene: β-galactosidase.
• y gene: permease.
• a gene: transacetylase.
• Lactose (or allolactose) acts as the inducer by binding the repressor.

Human Genome Project and DNA fingerprinting

Know the goals and key findings of the Human Genome Project, and the principle of DNA fingerprinting using repetitive DNA.

Evolution

• Origin of life: theories and the Miller-Urey experiment.
• Evidence: fossils, homologous and analogous organs, and adaptive radiation such as Darwin's finches.
• Natural selection: industrial melanism as an example.
• Hardy-Weinberg principle: p² + 2pq + q² = 1, and the five factors that disturb equilibrium: gene migration, genetic drift, mutation, genetic recombination and natural selection.
• Human evolution: the sequence of hominids as given in NCERT.

How to practise genetics problems

1. Write the genotypes of the parents first.
2. Draw a Punnett square for anything beyond a simple cross.
3. Check whether the question asks for phenotypic or genotypic ratio.
4. For pedigrees, test each inheritance pattern against the chart.
5. Solve PYQs, then mixed problem sets.

Frequently asked questions

Is genetics hard for NEET?

The problems become routine with practice. Most use a small set of standard ratios and patterns.

Which part of genetics is asked most?

Genetic disorders, Mendelian ratios, the lac operon and steps of the central dogma are common.

How should I revise Evolution?

Read NCERT closely, since many questions are factual, and practise Hardy-Weinberg calculations.

The short version

Learn the standard Mendelian ratios, sex determination systems and a disorder table. Know replication, transcription, translation and the lac operon in detail. Revise Evolution from NCERT and practise Hardy-Weinberg and pedigree problems with PYQs.

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