amazon.co.ukGenetics and Inheritance
A-Level Biology revision: Genetics and Inheritance. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.
📌 Key Points
Key Fact: DNA: antiparallel strands, complementary base pairing (A-T, G-C), sugar-phosphate backbone; Replication: helicase, DNA polymerase, Okazaki fragments, ligase
Key Fact: Transcription: RNA pol, promoter, mRNA; Translation: tRNA, ribosome, codon-anticodon, start/stop codons; Eukaryotes: splicing (introns/exons), 5' cap, poly-A tail
Key Fact: Mendel: segregation, independent assortment; Punnett squares; Test cross: unknown x homozygous recessive
Key Fact: Linkage: genes on same chromosome; recombination frequency ∝ distance; Epistasis: one gene masks another (e.g. 9:3:4, 12:3:1, 9:7 ratios)
Key Fact: Chi-squared: χ^2 = Σ(O-E)^2/E; df = n-1; p>0.05 = accept null (observed = expected)
Key Fact: Mutations: substitution (silent/missense/nonsense), insertion/deletion (frameshift); Chromosomal: deletion, duplication, inversion, translocation, non-disjunction
🎯 Learning Objectives
- Describe DNA structure, replication (semi-conservative), and the genetic code
- Explain transcription, translation, and post-transcriptional modification
- Apply Mendelian genetics: monohybrid, dihybrid, test crosses
- Understand gene linkage, crossing over, and epistasis
- Apply chi-squared test to genetic ratios
- Describe mutations: gene (point, frameshift) and chromosome (structural, numerical)
💡 Worked Example
Exam-Style Question
Question: In sweet peas, flower colour is controlled by two genes (C and P). Both dominant alleles needed for purple flowers. Cross CcPp x CcPp. Find phenotypic ratio
Model Answer:
Both genes needed for purple. C_P_ = purple (9/16); ccP_ = white (3/16); C_pp = white (3/16); ccpp = white (1/16). Ratio = 9 purple : 7 white (complementary epistasis)
❓ Practice Questions
Model answers are being added progressively - questions marked ✗ don't have one yet. Cross-check with your teacher or the official mark scheme.
Questions:
- Describe semi-conservative replication✗ answer coming soon
- A cross gives 9:3:3:1. What does this indicate?✗ answer coming soon
- Chi-squared test: observed 52:18, expected 3:1 ratio. Calculate χ^2✗ answer coming soon
- Explain how a frameshift mutation affects protein✗ answer coming soon
🎬 Video Resources
- Genetics and Inheritance - Overview -- YouTube Search
- Genetics and Inheritance - Exam Questions -- YouTube Search
📄 Past Papers & Exam Resources
🔗 Further Reading & Resources
- Physics & Maths Tutor - Genetics and Inheritance -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths - Genetics and Inheritance -- Free resources, slides, and interactive questions
- BBC Bitesize - Genetics and Inheritance -- BBC Bitesize revision resources