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Playbook

Genetics and Evolution

4 q · 0% HARD in 10 years. Heredity and DNA (3 · base pairing A-T/G-C, DNA structure facts), Theory of Evolution (1 · Darwin/Origin of Species). The smallest chapter — drill the 4 q in one sitting; don't over-invest, no return on time.

questions in the bank
4
tagged HARD
0%
subtopic(s)
2
worked examples
2

When you’ll see it

A DNA-base-pairing question (A-T and G-C), a heredity-principle question (gene/allele/chromosome basics), or a 'who proposed/wrote X' question (Darwin/Origin of Species).

How this chapter is tested

4 q in 10 years, ZERO HARD. The smallest NDA Biology chapter. Heredity and DNA (3 q): the genetic-material questions test base pairing rules — adenine pairs with thymine (A-T, 2 H-bonds), guanine pairs with cytosine (G-C, 3 H-bonds); the double helix has antiparallel strands; humans have 46 chromosomes (23 pairs); chromatin = DNA + histone proteins.

Theory of Evolution (1 q): Darwin's 'On the Origin of Species by Means of Natural Selection' (1859) is the textbook reference. Lamarck (1809) proposed inheritance of acquired characteristics (rejected). Mendel (1865) established laws of inheritance from pea-plant experiments (Law of Segregation, Law of Independent Assortment). Watson + Crick (1953) — DNA double helix structure.

Don't over-invest in this chapter — 4 q across 10 years = 0.4 q per year on average. Read once in 30 min, recognise on test day, move on. The bigger chapter for inheritance content is Reproduction (Sexual Reproduction — Genetic Principles, 3 q).

The sub-skills

The rules and habits that decide whether you get a question right.

  • DNA base-pairing rules

    A (adenine, purine) pairs with T (thymine, pyrimidine) via 2 H-bonds. G (guanine, purine) pairs with C (cytosine, pyrimidine) via 3 H-bonds. Strands are antiparallel (5'→3' opposite to 3'→5'). In RNA, T is replaced by U (uracil). Total purine = total pyrimidine (Chargaff's rule).

  • Chromosome arithmetic

    Humans: 46 chromosomes = 23 pairs (22 autosomes + 1 sex pair). Gametes (egg, sperm) = 23 chromosomes (haploid). Zygote = 46 (diploid). XX = female, XY = male. Down syndrome = trisomy 21 (3 copies of chromosome 21).

  • Evolution + heredity authorship

    Darwin (1859) → Origin of Species, natural selection. Mendel (1865) → laws of inheritance from pea plants. Lamarck (1809) → inheritance of acquired characteristics (refuted). Watson + Crick (1953) → DNA double helix. Morgan → chromosome theory of inheritance (fruit flies).

2 worked examples from the bank

Real past-year questions illustrating the playbook. Click to reveal options + solution.

Example 1Genetics and EvolutionEASY
The book The Origin of Species by Means of Natural Selection was authored by

[Q131 · Sep · 2025]

Example 2Genetics and EvolutionEASY
Which is the correct base pairing found in a normal DNA molecule?

[Q110 · Apr · 2025]

Traps to expect

Distractor shapes specific to this chapter. The page-wide Traps section covers the bank-level patterns.

  • A pairs with G

    Wrong. A always pairs with T (DNA) or U (RNA). G always pairs with C. Distractor swaps the pairings or pairs purine-with-purine. The 2025 PYQ tests exactly this — 'normal DNA base pairing' is A-T and G-C.

  • Lamarck wrote Origin of Species

    DARWIN wrote 'On the Origin of Species' (1859). Lamarck proposed an EARLIER and now-rejected theory of inheritance of acquired characteristics (1809). Distractor swaps the authors. Mendel founded modern genetics with pea-plant experiments (1865).

Drill every genetics and evolution question

4 questions from the bank, scoped to 2 bundled subtopics.

Drill the 4 questions

Related playbooks

Often paired with this one — drill these next if you found the worked examples above tractable.