A-Level Biology: Genetics and Inheritance Lesson-by-Lesson Breakdown

This scheme of work turns the genetics and inheritance portion of A-level Biology into a structured sequence of lessons. It is based on the common content found across major specifications, especially DNA and genes, variation, inheritance patterns, population genetics, evolution, and modern genetic technologies.

Suggested teaching sequence: start with DNA and gene expression, move into meiosis and variation, then inheritance patterns and genetic maths, before finishing with population genetics, evolution, and applied genetics.

Course Overview

Recommended Length

10 lessons, each designed as a single teaching block.

Main Curriculum Areas

DNA and genes, protein synthesis, mutation, meiosis, variation, inheritance, chi-squared, Hardy-Weinberg, evolution, and genetic technology.

Lesson-by-Lesson Plan

Lesson 1

DNA, Genes and Chromosomes

Focus: the structure and organisation of genetic material.

Core content

  • DNA structure and the idea of genes as sections of DNA
  • Chromosomes in eukaryotes and circular DNA in prokaryotes
  • The meaning of locus
  • The universal, degenerate, non-overlapping genetic code

Lesson outcomes

  • Define gene, chromosome, genome and locus
  • Explain how base sequence stores genetic information
  • Compare prokaryotic and eukaryotic DNA organisation
Lesson 2

Transcription, Translation and Protein Synthesis

Focus: how genes are expressed to produce proteins.

Core content

  • mRNA and tRNA structure
  • Transcription and the role of RNA polymerase
  • Pre-mRNA splicing in eukaryotes
  • Translation at the ribosome

Lesson outcomes

  • Describe the stages of transcription and translation
  • Link codons to amino acid sequence
  • Explain how genes determine phenotype through protein production
Lesson 3

Mutation and Sources of Genetic Variation

Focus: where new alleles and variation come from.

Core content

  • Gene mutations such as base substitution and deletion
  • Chromosome mutation and non-disjunction
  • Mutagenic agents
  • Why not all mutations change amino acid sequence

Lesson outcomes

  • Explain how mutation creates new alleles
  • Distinguish between gene and chromosome mutation
  • Predict possible effects of mutations on proteins and phenotype
Lesson 4

Meiosis and Genetic Diversity

Focus: how meiosis increases variation in offspring.

Core content

  • Two divisions producing four haploid daughter cells
  • Independent segregation of homologous chromosomes
  • Crossing over between homologous chromosomes
  • Random fertilisation as an extra source of diversity

Lesson outcomes

  • Explain how meiosis differs from mitosis
  • Show how meiosis produces non-identical gametes
  • Use chromosome diagrams to model meiotic outcomes
Lesson 5

Genotype, Phenotype and Basic Inheritance

Focus: the language and rules of inheritance.

Core content

  • Genotype and phenotype
  • Dominant, recessive and codominant alleles
  • Homozygous and heterozygous genotypes
  • The role of environment in phenotype

Lesson outcomes

  • Use inheritance vocabulary accurately
  • Explain the difference between genotype and phenotype
  • Recognise how environment can influence phenotype
Lesson 6

Monohybrid, Dihybrid and Sex-Linked Crosses

Focus: predicting inheritance patterns using genetic diagrams.

Core content

  • Monohybrid crosses
  • Dihybrid crosses
  • Sex linkage and autosomal linkage
  • Multiple alleles and epistasis where required by board

Lesson outcomes

  • Construct fully labelled genetic diagrams
  • Predict expected genotypic and phenotypic ratios
  • Interpret sex-linked inheritance patterns
Lesson 7

Chi-Squared and Probability in Genetics

Focus: testing whether observed inheritance patterns fit expectation.

Core content

  • Probability in monohybrid and dihybrid crosses
  • Observed versus expected ratios
  • Using the chi-squared test for goodness of fit
  • Interpreting significance in genetic data

Lesson outcomes

  • Calculate expected ratios and probabilities
  • Carry out a chi-squared test
  • Draw conclusions from inheritance data
Lesson 8

Population Genetics and Hardy-Weinberg

Focus: how allele frequencies behave in populations.

Core content

  • Population, gene pool and allele frequency
  • Hardy-Weinberg principle and its assumptions
  • Calculating allele, genotype and phenotype frequencies
  • Using Hardy-Weinberg to detect change over time

Lesson outcomes

  • Define allele frequency clearly
  • Use p² + 2pq + q² = 1 in exam-style questions
  • Explain what it means when a population is not in equilibrium
Lesson 9

Natural Selection, Genetic Drift and Speciation

Focus: how variation and inheritance drive evolution.

Core content

  • Natural selection and differential reproductive success
  • Directional, stabilising and disruptive selection
  • Genetic drift in small populations
  • Isolation, reproductive separation and speciation

Lesson outcomes

  • Explain how allele frequencies change over generations
  • Compare natural selection and genetic drift
  • Describe how new species can arise from existing species
Lesson 10

Applied Genetics and Genetic Technologies

Focus: modern uses of genetics in biology and medicine.

Core content

  • Epigenetics
  • DNA profiling
  • PCR and gel electrophoresis
  • Genetic screening, genome sequencing and genetically modified organisms
  • Social and ethical issues in modern genetics

Lesson outcomes

  • Describe key modern genetic techniques
  • Explain biological applications of genetic technology
  • Evaluate benefits, limitations and ethical concerns

Optional Additions

Assessment lesson

Add a final revision or assessment lesson with mixed exam questions on crosses, chi-squared, Hardy-Weinberg, and evolution.

Practical links

Where your specification allows, connect lessons to modelling inheritance ratios, sampling populations, or DNA-based practical work.

Sources

This page can be saved directly as lesson-breakdown.html.