Watch first
▶
MyGCSEScience · AQA Biology
DNA & the Genome — watch on MyGCSEScience
↗
FreeScienceLessons · AQA BiologyDNA and the Genome
Key facts
DNA structure
- DNA = double helix structure. Two strands of nucleotides wound around each other.
- Each nucleotide contains: a sugar (deoxyribose), a phosphate group, and one of four bases.
- Complementary base pairs: A–T (adenine–thymine) and C–G (cytosine–guanine).
- The bases pair by hydrogen bonds. The specific pairing means DNA can be replicated accurately.
- DNA is found in the nucleus of eukaryotic cells, coiled into chromosomes.
Genes and the genome
- Gene = a section of DNA that codes for a specific protein.
- Genome = the entire DNA of an organism — all the genetic information.
- The Human Genome Project mapped all ~3 billion base pairs of human DNA.
- Importance: identify genes linked to disease, develop targeted treatments, understand inheritance.
- Protein synthesis: DNA base sequence → (transcription) → mRNA → (translation at ribosome) → protein.
- A change in DNA base sequence = mutation. May change the protein produced.
Exam questions — 3 questions · 9 marks
⚡ Extended questions included. Read the hint. Write in full sentences. AI marks against the AQA mark scheme.
1 markComplementary base pairingAQA 8461 style
A section of DNA has the sequence ATCGGA. What is the complementary base sequence on the other strand?
A ATCGGA
B TAGCCT
C UAGCCU
D TACGGT
4 marksProtein synthesis chainAQA 8461 P2 style
Describe the process by which DNA is used to synthesise a protein. (4 marks)
Hint: Two stages: transcription (DNA → mRNA in nucleus) → translation (mRNA → protein at ribosome). Mention codons and amino acids.
+40 XP
1 markGenome significanceAQA 8461 style
Why is knowledge of the human genome important for medicine?
A It allows scientists to create new genetic mutations deliberately
B It allows identification of genes associated with inherited diseases, enabling earlier diagnosis and development of targeted treatments
C It means all genetic diseases can now be cured by gene therapy
D It replaces the need for clinical trials
Module complete! 🎉
Score loading...