Lesson 2.2.2

2.2.2 Transcription, translation, the genetic code and genes 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 2.2.2, Transcription, translation, the genetic code and genes: 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. Which enzyme catalyses the synthesis of messenger RNA during transcription?

    • DNA polymerase
    • Peptidyl transferase
    • Helicase
    • RNA polymerase

  2. Which strand of DNA is used as the template for transcription?

    • The antisense (template) strand
    • Neither strand; mRNA is made from free amino acids
    • Both strands are transcribed at the same time in every gene
    • The sense (coding) strand

  3. Which base is found in mRNA but not in DNA?

    • Guanine
    • Uracil
    • Adenine
    • Thymine

  4. What is the codon for the start of translation?

    • UAA
    • UAG
    • UGA
    • AUG

  5. Which of these is a stop codon?

    • CUU
    • UAG
    • GGC
    • AUG

  6. What is the anticodon on a tRNA molecule that is complementary to the codon AUG?

    • GUA
    • UAC
    • AUG
    • TAC

  7. Which description of the genetic code is correct?

    • It is a triplet code, read in groups of three bases called codons
    • It is a doublet code, read in groups of two bases called codons
    • It is a quadruplet code, read in groups of four bases called anticodons
    • It is a single-base code, read one base at a time from the DNA

  8. What does it mean to say the genetic code is non-overlapping?

    • Each base is used in two codons, so codons overlap along the mRNA
    • Different genes can share the same codons, so the code overlaps between genes
    • Each base belongs to only one codon, and codons are read consecutively without sharing bases
    • Two codons can code for different amino acids, depending on the reading frame at the start

  9. What does it mean to say the genetic code is degenerate?

    • Some codons code for no amino acid and are never used in any protein
    • More than one codon can code for the same amino acid
    • Each codon codes for a unique amino acid, but some bases are missing
    • The code is damaged by mutation, so it no longer reliably codes for amino acids

  10. How many possible codons are there with four different bases read in triplets?

    • 16
    • 20
    • 64
    • 32

  11. A DNA template strand has the sequence 3'-TACGGC-5'. What is the sequence of the mRNA produced by transcription, written 5' to 3'?

    • 5'-AUGCCG-3'
    • 5'-GCCGUA-3'
    • 5'-TACGGC-3'
    • 5'-ATGCCG-3'

  12. A polypeptide has 100 amino acids. What is the minimum number of nucleotides in the coding sequence of its mRNA, excluding the stop codon?

    • 400
    • 100
    • 200
    • 300

  13. What is the role of the ribosome in translation?

    • It attaches the amino acid to tRNA using ATP, before transcription begins
    • It joins Okazaki fragments together to form a continuous strand of DNA during replication
    • It unwinds the DNA double helix so that the template strand is exposed for transcription
    • It binds mRNA and tRNA, and it catalyses peptide bond formation between amino acids

  14. What is the function of tRNA in translation?

    • It carries a specific amino acid and has an anticodon that pairs with the mRNA codon
    • It forms peptide bonds directly between amino acids, acting as the catalyst of translation
    • It unwinds the mRNA so that the ribosome can read each codon in the correct order
    • It carries the genetic information from the nucleus to the ribosome as a template strand

  15. Which of these describes a gene?

    • A single base on a DNA molecule that determines the colour of an organism
    • A sequence of amino acids that folds to form a functional enzyme in the cytoplasm
    • A molecule of RNA that carries amino acids to the ribosome for translation
    • A sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide

  16. Why does a point mutation that changes a codon from GAA to GAG often have no effect on the protein?

    • Both codons code for glutamate, so the amino acid sequence is unchanged because of degeneracy
    • The mutation occurs in the intron, which is always removed before translation begins
    • Both codons are start codons, so the protein is produced from the same position in the mRNA
    • Both codons code for stop signals, so translation is halted at the same point in each case

  17. A mutation changes a codon from UUU to UAA. What is the most likely effect on the polypeptide?

    • Translation stops early, producing a shorter polypeptide
    • No effect, because both codons are part of the same genetic code
    • The amino acid changes from phenylalanine to another amino acid only
    • The polypeptide becomes longer, because the new codon adds an extra amino acid

  18. Which of these best describes the difference between transcription and translation?

    • Transcription makes a polypeptide from mRNA, whereas translation makes DNA from mRNA
    • Transcription and translation both make DNA from amino acids in the nucleus
    • Transcription makes mRNA from DNA, whereas translation makes a polypeptide from mRNA
    • Transcription makes DNA from RNA, whereas translation makes mRNA from a polypeptide

  19. In translation, a ribosome moves along an mRNA molecule. Which event happens at the start of translation?

    • The ribosome binds to the stop codon, and the polypeptide is released from the ribosome
    • The ribosome binds to the mRNA at the start codon, and the first tRNA with the matching anticodon binds
    • The DNA double helix is rejoined by DNA ligase at the ribosome
    • The ribosome breaks the peptide bonds between the amino acids in the growing chain

  20. Why is it important that the genetic code is nearly universal across organisms?

    • It means that all organisms have identical DNA sequences in every gene, so genetic variation between individuals cannot occur
    • It means the same codons specify the same amino acids in most organisms, so genes can be transferred and expressed in other species
    • It means all organisms use the same proteins in the same proportions, so no variation exists between any species at all
    • It means that no mutation can ever alter the amino acid sequence of any protein in any organism, whatever the cause

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