Speciation and genetics extra: GCSE Biology
DNA bases, protein synthesis, mutations, speciation, evolution evidence and genetic engineering
The short version
Complementary bases, transcription and translation, mutations, geographic isolation and speciation, plus genetic engineering.
Key idea
Hydrogen bonds hold the pair (name optional); sequence is the information
Grade 2–3: DNA letters stick to their partners: A with T, C with G.
Grade 5–6: I can draw a short complementary strand and say double helix.
Grade 9: I use genome correctly and I never say A pairs with C. I can say a gene is a section of DNA that codes for a protein (or polypeptide).
Go a bit deeper
Triplet = three bases → one amino acid
Grade 2–3: DNA tells the cell which protein to build, letter by letter.
Grade 9: I keep DNA in the nucleus, U not T in RNA, and I link sequence to shape. I do not say the ribosome is in the nucleus.
Question: Why can a base-change mutation stop an enzyme working? [3 marks] [3 marks]
Worked example
Worked example
Grade 2–3: DNA letters stick to their partners: A with T, C with G. Grade 5–6: I can draw a short complementary strand and say double helix. Grade 9: I use genome correctly and I never say A pairs with C. I can say a gene is a section of DNA that codes for a protein (or polypeptide).
Lessons in this topic
- DNA structure extra
- Protein synthesis
- Mutations
- Speciation
- Evidence for evolution extra
- Genetic engineering
In the app each lesson is video (when we have a real YouTube id) then intro, learn and summary steps.
What the examiner wants
Recall base pairing, outline protein synthesis (HT), explain speciation, and evaluate genetic engineering examples such as insulin.
Try these questions
Cover the answers and have a go first. Worked solutions are underneath.
In DNA, adenine pairs with
The complementary strand to GGA is
Transcription produces
Translation happens at the
Common mistakes
- A does not pair with C. Mixing the pairs wrecks replication and protein-synthesis questions.
- Translation is not "the DNA turns into a protein". DNA is copied to mRNA; the protein is a different molecule.
- Mutations are not a response to antibiotics. The antibiotic selects resistant bacteria that already appeared by chance.
- Living on different islands is not speciation until they cannot produce fertile offspring. Isolation is the start, not the definition of a species.
Answers and working
Frequently asked questions
Is GCSE Speciation and genetics extra on Combined Science and Triple?
Speciation and genetics extra is Triple-only Biology. Combined Science students can skip it.
Which exam board is this Speciation and genetics extra page for?
The ideas are board-agnostic for AQA, Edexcel, OCR, WJEC and CCEA. Paper lengths and question numbers differ — check your specification.
Is Speciation and genetics extra Foundation or Higher?
The core ideas appear on both tiers. Higher papers add extra application and some HT-only detail, marked in lessons with a Higher badge.
Learn, try, get feedback, fix the mistake
Open the stepped lesson, then the quiz with hints. Required-practical and calculation questions use the same method you will need in the paper.
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