Lesson 2.4.2

2.4.2 Mutations and cystic fibrosis Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 2

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 2.4.2, Mutations and cystic fibrosis: 20 multiple choice questions for the Pearson Edexcel Biology A (Salters-Nuffield) (9BI0), Unit 2: Genes and Health, written with Revision Ninja.

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The 20 questions

  1. Cystic fibrosis is caused by mutations in the CFTR gene. What does the CFTR protein normally do?

    • It forms a structural protein in muscle fibres, which allows the muscle to contract
    • It carries haemoglobin in red blood cells, which transports oxygen to the tissues
    • It forms a chloride ion channel in cell membranes
    • It repairs DNA breaks in dividing cells, which protects the genome from damage

  2. Cystic fibrosis is inherited as which type of allele pattern?

    • Autosomal dominant
    • X-linked dominant
    • X-linked recessive
    • Autosomal recessive

  3. The most common CF mutation, deltaF508, is best described as which change?

    • Insertion of one base that shifts the reading frame for every later codon
    • Deletion of three bases, removing the codon for phenylalanine at position 508
    • Duplication of a whole chromosome region including the CFTR gene
    • Substitution of a single base that changes a codon into a stop codon

  4. Which type of mutation shifts the reading frame for every codon after the change?

    • Inversion of a sequence of three bases in place
    • Insertion or deletion of a number of bases that is not a multiple of three
    • Substitution of a single base within a codon
    • Deletion of exactly three consecutive bases

  5. What is a silent mutation?

    • A change that alters an amino acid and always reduces protein function
    • A change that stops translation at the first codon of the gene
    • A change that adds three bases to the coding sequence without altering the reading frame
    • A change in a codon that still codes for the same amino acid

  6. Which of these is a mutagen?

    • Sodium chloride in table salt
    • Vitamin C in citrus fruit
    • Glucose in the blood plasma
    • Ionising radiation such as X-rays

  7. Which cells must carry a mutation for it to be inherited by offspring?

    • Liver cells that carry out detoxification
    • Skin cells on the surface of the body
    • Gamete-producing cells, which give rise to sperm and egg cells
    • Neurons in the brain and spinal cord

  8. In healthy airways, what does the CFTR channel help move, and what follows?

    • Calcium ions into the cytoplasm, with water leaving through aquaporins to trigger contraction
    • Sodium ions into the cell, with water leaving by osmosis to thicken mucus
    • Chloride ions out of the cell, with water following by osmosis to keep mucus thin
    • Glucose into the cell by facilitated diffusion, with water entering by active transport

  9. Two carriers of the CF allele have a child. What is the probability that the child has cystic fibrosis?

    • 0%
    • 50%
    • 75%
    • 25%

  10. If 1 in 2500 people has cystic fibrosis, what is the approximate frequency of the recessive allele q, under Hardy-Weinberg assumptions?

    • 0.04
    • 0.25
    • 0.0004
    • 0.02

  11. A 3-base deletion occurs inside the coding region of a gene. What is the most likely result?

    • Loss of one amino acid, with the sequence on either side of the deletion otherwise unchanged
    • Immediate termination of translation at the mutation site
    • A frameshift that alters every amino acid downstream of the deletion
    • Doubling of the protein length because the reading frame is repeated

  12. A substitution changes the codon GAA into GAG. Both code for glutamate. What is the effect on the protein?

    • The reading frame shifts by one base for the rest of the gene
    • No change to the amino acid sequence
    • A new amino acid is inserted at the mutation site
    • Translation stops at the mutated codon

  13. A substitution converts the tyrosine codon UAU into the stop codon UAA. What is the likely result?

    • The protein is made at full length but folds in a different shape only
    • Translation terminates early, producing a shortened and usually non-functional protein
    • The protein is made with one extra amino acid at the end of the chain
    • No change, because UAA still codes for tyrosine in some cells

  14. Why are carriers of CF usually free of symptoms?

    • The mutant allele is on the X chromosome, so it is not expressed in heterozygotes
    • Carriers have two dominant alleles that cancel out the mutant allele
    • The mutant allele is deleted from the cells of heterozygous individuals
    • One normal CFTR allele produces enough functional channel protein for normal function

  15. Which sequence correctly explains how the deltaF508 mutation leads to thick mucus in the lungs?

    • Extra CFTR channels open, so mucus takes in too much water and swells until it blocks the airway
    • Sodium is pumped out of cells, so mucus becomes acidic and sticky, which damages the airway lining
    • Mucus-producing cells divide too quickly, so the secretion accumulates as dense protein deposits
    • Misfolded CFTR is degraded, so fewer chloride channels reach the membrane, less water enters the airway surface, and mucus becomes thick

  16. A somatic liver cell acquires a mutation during the person's life. Will this mutation be passed to their children?

    • Yes, because liver cells can give rise to sperm and egg cells
    • No, only mutations in gamete-producing cells are inherited by offspring
    • Yes, because every body cell contributes genetic material to the offspring
    • Only if the same liver cell mutates a second time before reproduction

  17. UV light can damage DNA. What is the characteristic effect of UV light on adjacent thymine bases?

    • They convert adenine into guanine in every cell that is exposed
    • They only damage DNA outside the nucleus, so the genome is protected
    • They can bond to each other, distorting the helix and causing errors during replication
    • They split the sugar-phosphate backbone without affecting the bases

  18. A 1-base deletion shifts the reading frame, and a stop codon appears five codons later. What is the most likely outcome?

    • No protein is made from the gene at all
    • A longer protein is produced with the same function as before
    • A normal protein is made, because deletions are always repaired
    • A truncated, non-functional protein is produced

  19. Which statement correctly describes a consequence of CF for the digestive system?

    • Pancreatic enzymes are over-produced and digest the lining of the gut
    • Thick mucus blocks pancreatic ducts
    • Excess bile dissolves the mucus in the small intestine, causing diarrhoea
    • Mucus blocks the oesophagus, so food cannot be swallowed at all

  20. What is a point mutation?

    • An exchange of genes between two non-homologous chromosomes
    • The deletion of an entire gene together with its promoter
    • A change in the number of whole chromosomes in a cell
    • A change in a single base pair of DNA

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