Topic 2: Genes and health - Edexcel A-Level Biology B overview

Topic 2 of Edexcel A-Level Biology B (specification 9BN0, the Salters-Nuffield course) is titled Genes and health. It is taught through the context of cystic fibrosis and develops the molecular genetics, enzymes and biotechnology used throughout the course. This page maps the four dot-point areas and how they are examined.

The four dot-point areas

DNA and protein synthesis

The structure of DNA and RNA, semi-conservative replication, the genetic code, and transcription and translation.

Gene mutation and cystic fibrosis

The nature of gene mutations, the faulty CFTR chloride channel, the effects on the lungs, digestion and reproduction, and the recessive inheritance of the condition.

Enzymes

Enzymes as catalysts, the lock-and-key and induced-fit models, the effects of temperature, pH, substrate and enzyme concentration, and competitive and non-competitive inhibition.

Gene technology and screening

Gene therapy, genetic screening and prenatal testing, the use of genetic information, and the social and ethical issues these raise.

How Topic 2 is examined

Topic 2 appears across all three papers and is revisited in the synoptic Paper 3. Expect precise recall of replication, transcription and translation, mutation and inheritance problems, enzyme rate graphs from the core practicals, and balanced ethical discussion. The CFTR context ties the molecular detail to a real disease.

How to study Topic 2

1. Drill the central dogma. Be fluent in replication, transcription and translation and the role of each molecule.
2. Practise genetics problems. Use genetic diagrams for recessive inheritance and carrier crosses.
3. Read enzyme graphs. Explain rate changes with temperature, pH and concentration, and identify denaturation and limiting factors.
4. Build ethical arguments. Weigh the benefits and concerns of gene therapy and screening.

Work through the dot points

Each dot point has a focused answer page with worked exam questions and cross-links: DNA and protein synthesis; gene mutation and cystic fibrosis; enzymes; and gene technology and screening.

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.