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Topic 3: The voice of the genome - Edexcel A-Level Biology B overview

An overview of Topic 3 of Edexcel A-Level Biology B (Salters-Nuffield, 9BN0), covering cell structure and the cell cycle, meiosis and fertilisation, stem cells and differentiation, and gene expression and epigenetics, and how the topic is examined.

Generated by Claude Opus 4.88 min read9BN0

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  1. The four dot-point areas
  2. How Topic 3 is examined
  3. How to study Topic 3
  4. Work through the dot points
  5. For the official specification

Topic 3 of Edexcel A-Level Biology B (specification 9BN0, the Salters-Nuffield course) is titled The voice of the genome. It explores how a single fertilised cell becomes a complex multicellular organism, building the cell biology and genetics used later in the course. This page maps the four dot-point areas and how they are examined.

The four dot-point areas

Cell structure and the cell cycle
The ultrastructure of eukaryotic and prokaryotic cells, the functions of organelles, and the cell cycle and mitosis.
Meiosis and fertilisation
The events of meiosis, how crossing over and independent assortment generate variation, the role of gametes and fertilisation, and how meiosis differs from mitosis.
Stem cells and differentiation
The types of stem cells, how cells become specialised and organise into tissues and organs, and the uses and ethics of stem cells.
Gene expression and epigenetics
The control of transcription by transcription factors, epigenetic modifications such as DNA methylation and histone modification, and how the environment affects phenotype.

How Topic 3 is examined

Topic 3 appears across all three papers and is revisited in the synoptic Paper 3. Expect organelle labelling and function, the stages of mitosis and meiosis, sources of variation, and balanced discussion of stem cell uses and ethics, plus explanations of how gene expression and epigenetics control differentiation.

How to study Topic 3

  1. Learn organelle functions. Be able to link each organelle to its role and recognise it on a diagram.
  2. Sequence the divisions. Order the stages of mitosis and meiosis and explain what happens to chromosomes in each.
  3. Explain variation. Use crossing over, independent assortment and random fertilisation.
  4. Connect expression to differentiation. Show how transcription factors and epigenetics switch genes on and off.

Work through the dot points

Each dot point has a focused answer page with worked exam questions and cross-links: cell structure and the cell cycle; meiosis and fertilisation; stem cells and differentiation; and gene expression and epigenetics.

For the official specification

Pearson publishes the full specification (9BN0), past papers and mark schemes at qualifications.pearson.com. Always revise from the current specification and Edexcel's own past papers.

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