DNA, genes and protein synthesis — Edexcel International GCSE Science (Double Award)
The genome, genes and chromosomes: where DNA is found in a cell, and how each gene codes for a particular protein.
Revision notes
1 short note, in the order of the specification. Each one in short:
The genome is the entire DNA of an organism. A gene is a section of a molecule of DNA that codes for a specific protein. Genes are located on chromosomes, which are long DNA molecules found in the nucleus. Each gene has a different base sequence, so each codes for a different protein, which helps decide the organism's characteristics.
Exam questions
3 exam-style questions (5 marks), each with its mark scheme.
Answer the questionsFlashcards
3 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of reproduction and inheritance on one page, so you can see where this subtopic fits.
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Quick check questions
What is a gene?
Show answer
A section of a molecule of DNA that codes for a specific protein.
What is the genome?
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The entire DNA of an organism.
Frequently asked questions
What is the difference between a gene, a chromosome and the genome?
A gene is a section of a molecule of DNA that codes for a specific protein. A chromosome is a long DNA molecule, found in the nucleus, with many genes along it. The genome is the entire DNA of an organism, including all of its genes and the rest of its DNA.
Written and checked against the Edexcel IGCSE Science Double Award (4SD0) specification · Updated October 2026