What you'll learn
How genetic information is stored, copied, and expressed (~12–16% of the exam).
The central dogma
DNA → RNA → protein.
- Replication: semiconservative; DNA polymerase builds 5'→3'.
- Transcription (nucleus): RNA polymerase makes mRNA from a DNA template; mRNA is processed (cap, tail, splicing).
- Translation (ribosome): tRNA reads codons (3 bases) → amino acids; start (AUG) and stop codons.
Gene regulation
- Prokaryotes: operons (e.g. lac operon — inducible).
- Eukaryotes: regulation at many levels (transcription factors, epigenetics/methylation, RNA processing). Differential gene expression explains how identical cells specialise.
Mutations
Point mutations (silent, missense, nonsense), insertions/deletions causing frameshifts. Mutations are the raw material for variation/evolution.
Biotechnology
PCR (amplify DNA), gel electrophoresis (separate by size), CRISPR (edit), transformation.
Exam tips
- Trace a base change through to its effect on the protein.
- Explain how regulation produces cell differentiation.
Common mistakes
- Mixing up transcription and translation locations/products.
- Forgetting frameshifts are usually more damaging than point mutations.