Lesson 3.4.2

3.4.2 Differential gene expression and the lac operon Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 3.4.2, Differential gene expression and the lac operon: 20 multiple choice questions for the Pearson Edexcel Biology A (Salters-Nuffield) (9BI0), Unit 3: Voice of the Genome, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What is differential gene expression?

    • The selective switching on and off of genes so that cells develop different structures and functions
    • Copying the DNA identically before each cell division
    • Changing the DNA sequence of genes during development
    • Using only one type of gene in every cell of an organism

  2. What is the role of messenger RNA in producing a protein?

    • It carries the copy of the gene's code
    • It carries amino acids to the cell membrane
    • It forms the membrane of the ribosome
    • It breaks down proteins in lysosomes

  3. In the lac operon of E. coli, what does the lac repressor do when lactose is absent?

    • It binds to RNA polymerase and carries it to the gene
    • It binds to the operator and blocks transcription of the lac genes
    • It breaks down lactose in the cytoplasm
    • It binds to the ribosome and stops translation

  4. What happens to the lac repressor when lactose is present in the cell?

    • The repressor is converted into lactose and removed
    • The repressor moves into the nucleus and binds the ribosome
    • Allolactose binds the repressor, which releases the operator so the genes are transcribed
    • The repressor is destroyed and the operon is permanently switched off

  5. Which enzyme is encoded by the lac operon and used to break down lactose?

    • Catalase
    • Amylase
    • Pepsin
    • Beta-galactosidase

  6. Why is the lac operon described as an inducible system?

    • Its genes are only active in plant cells
    • Its genes are switched on only when the cell is dividing
    • Its genes are switched off in all conditions
    • Its genes are switched on in the presence of an inducer such as lactose

  7. In the lac operon, what is the function of the operator?

    • It is the RNA that carries amino acids to the ribosome
    • It is the DNA sequence the repressor binds to, controlling access of RNA polymerase
    • It is the enzyme that breaks down lactose into glucose
    • It is the protein that forms the cell membrane

  8. How does differential gene expression explain why a muscle cell and a neuron are different?

    • They have the same DNA, but each expresses a different set of genes
    • They have different numbers of chromosomes
    • They have different DNA sequences from the zygote
    • They lose different genes during mitosis

  9. What is transcription?

    • Joining amino acids to form a polypeptide on a ribosome
    • Copying DNA before cell division
    • Making an mRNA copy of a gene from DNA
    • Breaking down proteins into amino acids

  10. What is translation?

    • Using the sequence of mRNA codons to join amino acids into a polypeptide on a ribosome
    • Breaking down mRNA into nucleotides
    • Joining two DNA strands together
    • Using DNA to make an RNA primer

  11. What is the advantage of the lac operon for a bacterium?

    • It switches on the enzymes for lactose use only when lactose is available, saving energy
    • It makes the bacterium resistant to all antibiotics
    • It allows the bacterium to make chloroplasts
    • It prevents any gene expression from taking place

  12. A mutation prevents the lac repressor from binding to the operator. What is the likely result?

    • The enzymes are made but the cell cannot take in lactose
    • The lac genes are transcribed continuously, even without lactose
    • The lac genes are never transcribed, even with lactose
    • The mRNA is destroyed as soon as it is made

  13. Which statement describes how a cell becomes specialised?

    • Specific genes are activated
    • The cell gains extra chromosomes from neighbouring cells
    • Cell division stops and the cell fills with water
    • Genes are deleted from the DNA as the cell matures

  14. Which molecule is an inducer of the lac operon?

    • Beta-galactosidase
    • Glucose
    • Lac repressor
    • Allolactose

  15. What would be expected if a researcher added a lactose analogue that cannot bind the repressor?

    • The repressor would be produced in greater quantity
    • The operon would be switched on immediately and strongly
    • The operon would stay switched off
    • The mRNA would be translated without ribosomes

  16. Which statement about gene expression in plants and animals is correct?

    • Animals express all genes equally in every cell
    • Plants use no differential gene expression because they lack a nucleus
    • Both use differential gene expression to produce specialised cells
    • Differential gene expression occurs only in bacteria

  17. In the lac operon, what is the role of the structural genes?

    • They encode the repressor that switches the operon off
    • They encode the ribosomes of the cell
    • They encode the enzymes needed to metabolise lactose
    • They encode the cell wall of the bacterium

  18. Why is a repressor protein described as negative control?

    • It switches gene expression off by binding DNA
    • It switches gene expression on by binding RNA polymerase
    • It switches on the operon only in the nucleus of eukaryotes
    • It switches off translation by degrading mRNA in the cytoplasm

  19. In an E. coli culture with lactose absent, what is the state of the lac operon?

    • It is switched on so that beta-galactosidase is made at high levels
    • It is destroyed by the presence of glucose in the medium
    • It stays switched off because the repressor is bound to the operator and no inducer is present
    • It is copied into mRNA but the mRNA is never translated

  20. Which DNA region is the binding site for RNA polymerase to start transcription?

    • The codon
    • The intron
    • The promoter
    • The operator

All Pearson Edexcel Biology A (Salters-Nuffield) quizzes