NDA Biology · Teaching notes
Genetics and Evolution — NDA Biology
Genetics and Evolution is a small chapter in NDA Biology — only a handful of PYQs across 2017–2026, all EASY or MODERATE, and all pure named-fact recall. Because the bank is thin, this chapter is built foundation-first: it teaches the whole topic from zero — what a gene is, how DNA is structured, how traits are inherited, and how species change over time — so a student (or a teacher using it as a lesson plan) gets the complete picture, not just the four questions that happen to have been asked. The chapter teaches in two movements: (1) Heredity and DNA — the gene as the unit of inheritance, the double-helix structure of DNA with its A–T and G–C base pairing, alleles and genotypes, Mendel's laws, and the scientists who cracked the structure; (2) Evolution — what evolution means and Darwin's theory of natural selection. Learn the base-pairing rule, the allele definition, the Watson–Crick–Wilkins story, and Darwin cold, and every PYQ in this chapter is free.
Subtopic notes
Heredity, DNA and Genes
3 PYQsHeredity is the passing of traits from parents to offspring through genes — segments of DNA, the double-helix molecule whose A–T and G–C base pairing carries all genetic information.
Open note
The Theory of Evolution
1 PYQsEvolution is the gradual change in the heritable characteristics of a population over many generations; Darwin explained it through natural selection — the survival and reproduction of the best-adapted individuals.
Open note
PYQ weightage by concept
7 concepts · 4 PYQs — where the marks actually sit, so you know what to drill first
PYQ weightage by concept
7 concepts · 4 PYQs — where the marks actually sit, so you know what to drill first
| Concept | PYQs | Share |
|---|---|---|
| DNA structure and base pairing | 1 | 25% |
| Genes, alleles and genotype | 1 | 25% |
| Who discovered the structure of DNA | 1 | 25% |
| Heredity — genes, chromosomes and DNAfoundation | — | — |
| Mendel's laws of inheritancefoundation | — | — |
| Concept | PYQs | Share |
|---|---|---|
| Darwin and natural selection | 1 | 25% |
| What evolution meansfoundation | — | — |
Formula & revision sheet
1 formulas · 1 reference tables · 7 gotchas across all subtopics — the exam-eve cheat-sheet
Formula & revision sheet
1 formulas · 1 reference tables · 7 gotchas across all subtopics — the exam-eve cheat-sheet
Reference tables (1)
Who discovered the structure of DNA4 rows
| Scientist | Contribution |
|---|---|
| James Watson & Francis Crick | Built the double-helix model of DNA (1953) |
| Maurice Wilkins | X-ray diffraction studies of DNA; shared the 1962 Nobel Prize Wilkins is the name the 1962-Nobel question asks for — alongside Watson and Crick. |
| Rosalind Franklin | X-ray photograph ('Photo 51') that revealed the helix; died 1958, so not in the 1962 prize |
| Erwin Chargaff | Chargaff's rules — in DNA, A = T and G = C |
Watch out for (5)
- A pairs with T, not with G or C→ DNA structure and base pairing
- G–C has 3 hydrogen bonds, A–T has 2→ DNA structure and base pairing
- Allele vs genotype vs isomer→ Genes, alleles and genotype
- 3 : 1 is the phenotype ratio, 1 : 2 : 1 is the genotype ratio→ Mendel's laws of inheritance
- Franklin and Chargaff are the distractors in the 1962-Nobel question→ Who discovered the structure of DNA
Watch out for (2)
- Darwin wrote 'The Origin of Species' — not Linnaeus or Lamarck→ Darwin and natural selection
- Darwin vs Lamarck→ Darwin and natural selection