Who this is for: Cambridge IGCSE Biology (0610) students who want chromosomes, genes and proteins — DNA structure, base pairing and protein synthesis — to become reliable marks instead of a diagram they can label but not explain.
What query it owns: how to understand and revise chromosomes, genes and proteins in Cambridge IGCSE Biology.
Why this is safe: this page owns the chromosomes-genes-proteins revision-guide angle, while Tutopiya’s Chromosomes, Genes and Proteins subtopic page owns the learning resource and the free Chromosomes, Genes and Proteins quiz owns the practice.

Chromosomes carry genes made of DNA; genes code for proteins that determine an organism’s characteristics. Cambridge IGCSE Biology (0610) tests DNA structure, complementary base pairing, the relationship between genes and proteins, and the outline of protein synthesis. This guide covers the syllabus definitions, the structure tables examiners expect, and the question types that appear every year.

Key takeaways

• A chromosome is a thread-like structure of DNA and protein found in the nucleus; humans have 46 (23 pairs) in body cells.
• A gene is a section of DNA that codes for a specific protein.
• DNA is a double helix with complementary base pairing: A–T and C–G.
• Protein synthesis: DNA → mRNA (transcription in nucleus) → protein (translation at ribosomes).
• The sequence of bases in a gene determines the sequence of amino acids in the protein.

What are chromosomes, genes and proteins in Cambridge IGCSE Biology?

Chromosomes are found in the nucleus and contain DNA wrapped around proteins. Each gene is a specific sequence of DNA bases that codes for one protein. Proteins are chains of amino acids that form enzymes, structural components and other functional molecules. The relationship is: chromosome contains many genes → each gene codes for one protein → proteins determine characteristics.

You can read the full explanation, diagrams and notes on Tutopiya’s Chromosomes, Genes and Proteins subtopic page before you attempt questions.

The core ideas you must master

Idea	What it means	How the exam uses it
Chromosome	DNA + protein in nucleus	”State where chromosomes are found.”
Gene	Section of DNA coding for a protein	”Define gene.”
DNA double helix	Two strands twisted together	”Describe the structure of DNA.”
Base pairing	A–T, C–G complementary pairs	”State complementary base pairs.”
Protein synthesis	DNA → mRNA → protein	”Outline protein synthesis.”

DNA structure and base pairing

Component	Description
Shape	Double helix (two strands twisted)
Strands	Made of nucleotides
Nucleotide parts	Sugar, phosphate, base
Four bases	Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
Pairing rules	A pairs with T; C pairs with G
Bond type	Weak hydrogen bonds between base pairs

From gene to protein

Stage	Location	What happens
Transcription	Nucleus	DNA template used to make mRNA
mRNA	Leaves nucleus	Carries genetic code to cytoplasm
Translation	Ribosomes	mRNA code used to assemble amino acids into protein
Result	—	Protein with specific function (e.g. enzyme)

Chromosomes, genes and proteins in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical stem
Define	Precise syllabus definition	”Define the term gene.”
State	Short factual answer	”State the complementary base pair of adenine.”
Describe	Structure or process	”Describe the structure of a DNA molecule.”
Outline	Brief account of process	”Outline how a gene codes for a protein.”
Explain	Cause and effect	”Explain how a change in DNA base sequence can affect a protein.”

Worked exam-style stems (how to answer the wording)

1. “State the complementary base pairs in DNA.” Adenine (A) pairs with thymine (T); cytosine (C) pairs with guanine (G). Mark-scheme reward: both pairs named correctly.
2. “Define the term gene.” A gene is a length of DNA that codes for a specific protein. Reward: DNA + codes for + protein.
3. “Outline how a gene codes for a protein.” The DNA base sequence in a gene is copied to mRNA in the nucleus (transcription); mRNA moves to ribosomes where the base sequence determines the order of amino acids assembled into a protein (translation). Reward: transcription + translation linked.

When you can recognise the wording instantly, work the full set on Tutopiya’s Chromosomes, Genes and Proteins quiz and drill Inheritance for allele and gene terminology.

How chromosomes, genes and proteins connect to the rest of the syllabus

This topic links to Inheritance (alleles on chromosomes), Mitosis (chromosome duplication) and Enzymes (proteins as enzymes). The Cambridge IGCSE Biology resource hub links every Inheritance subtopic.

Common mistakes students make

• Pairing A with C or G with T (correct pairs are A–T and C–G).
• Saying genes are made of protein (genes are made of DNA; they code for proteins).
• Confusing transcription (DNA → mRNA, in nucleus) with translation (mRNA → protein, at ribosomes).
• Stating chromosomes are found in the cytoplasm (they are in the nucleus).
• Omitting that a gene codes for a protein in gene definitions.

When you need more support

If DNA structure questions keep costing marks — especially base pairing and protein synthesis outline stems — work through the Chromosomes, Genes and Proteins quiz, then get focused help from a Cambridge IGCSE Biology tutor.

Frequently asked questions

Are chromosomes, genes and proteins hard in Cambridge IGCSE Biology? DNA structure is straightforward once base pairing is memorised, but marks are lost on transcription vs translation and incomplete gene definitions.

What is the difference between a chromosome and a gene? A chromosome is a long DNA molecule containing many genes; a gene is one section of DNA that codes for one protein.

How many chromosomes do human body cells have? 46 chromosomes arranged in 23 pairs.

How do I revise chromosomes, genes and proteins effectively? Learn base pairing rules, practise gene definitions, outline protein synthesis from memory, then take the Chromosomes, Genes and Proteins quiz.

Ready to master Cambridge IGCSE Biology chromosomes, genes and proteins?

Start with the Chromosomes, Genes and Proteins subtopic page, then book a free trial with a Cambridge IGCSE Biology specialist to turn DNA and protein synthesis into guaranteed marks.

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