A LevelBiologyCIEExam Questions6. Nucleic Acids & Protein Synthesis6.2 Protein Synthesis

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First exams 2025

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Protein Synthesis (CIE A Level Biology)

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6.2 Protein Synthesis

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6.2 Protein Synthesis

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11 mark

Which enzyme is required for transcription?

  • Helicase

  • RNA polymerase

  • DNA ligase

  • DNA polymerase

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21 mark

Name the molecule that is the end product of translation.

  • tRNA

  • mRNA

  • polypeptide

  • amino acid

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31 mark

Sickle cell disease is caused by a change in the DNA sequence. The haemoglobin of affected people has a valine amino acid in its straight beta chain rather than glutamic acid.

What is the minimum number of base substitutions required to change the normal haemoglobin allele to the sickle cell allele?

  • 1

  • 2

  • 3

  • 4

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41 mark

In a genetic engineering experiment a piece of double-stranded DNA containing 18000 nucleotides coding for a specific polypeptide is transcribed and translated.

What is the maximum number of amino acids in this polypeptide?

  • 3000

  • 6000

  • 9000

  • 18000

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51 mark

This diagram shows two of polynucleotide strands.

image

State the name of strand 2.

  • tRNA

  • ribosomal RNA 

  • DNA

  • mRNA

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61 mark

Which statement describes a process that occurs during protein synthesis?

  • Translation is the synthesis of an mRNA molecule by base pairing of nucleotides with DNA.

  • RNA polymerase catalyses formation of covalent bonds in transcription. 

  • Transcription is the linking together of amino acids coded by mRNA.

  • Transcription is the linking together of free DNA nucleotides.

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71 mark

Which of the following biological molecules are required for translation? 

  • amino acids, DNA and ribosomes

  • ribosomes, mRNA and protein synthase

  • mRNA, RNA polymerase and ribosomes

  • ribosomes, mRNA and tRNA

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81 mark

In a DNA molecule, the base sequence TGT codes for the amino acid threonine.

What is the base sequence of the anti-codon on the tRNA to which threonine becomes attached?

  • UCU

  • TGT

  • ACA

  • UGU

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91 mark

A length of double-stranded DNA contains 180 nucleotides and codes for enzyme Z. 

What is the maximum number of amino acids in enzyme X?

  • 30

  • 60

  • 180

  • 540

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101 mark

The protein p53 is also known as the ‘Guardian of the Genome’.  It is produced in response to DNA damage and helps prevent the formation of tumours.  

Which of these could lead to an increase in the production of p53 in the body?

1 X-rays
2 Sunbeds
3 Smoking

  • 1, 2 and 3

  • 1 and 2 only

  • 2 and 3 only

  • 1 and 3 only

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11 mark

A piece of DNA was analysed to find the number of nucleotide bases in each of the polynucleotide strands.

Some of the results are shown below:

  number of nucleotide bases


Strand 1
Strand 2

 A


 T
30
30		 G
22
38		 C

What is the maximum number of amino acids that could be coded for by this DNA? 

  • 22

  • 29

  • 34

  • 40

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21 mark

What is the correct sequence for the processes involved in the formation of a protein? 

  • transcription → peptide bonding → translation → ionic bonding   

  • transcription → translation → peptide bonding → hydrogen bonding

  • transcription → peptide bonding → translation → hydrogen bonding

  • translation → peptide bonding → transcription → ionic bonding   

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31 mark

What terminates the formation of a polypeptide chain during protein synthesis in cells?

  • when the ribosome reaches the end of the mRNA molecule

  • when there are no more tRNA molecules 

  • when the ribosome reaches a stop codon on the mRNA

  • RNA polymerase detaches the polypeptide chain from the ribosome

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41 mark

DNA is composed of two strands, the transcribed strand and the non-transcribed strand.

Here is a section of DNA:

image-1

What would the corresponding mRNA sequence be for this section of DNA?

  • T A C A C C G A T G C T C

  • A U G U G G C U A C G A G

  • A T G T G G C T A C G A G

  • U A C A C C G A U G C U C

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51 mark

If a polypeptide chain is comprised of 200 amino acids, it might be expected that the coding gene in the DNA would be comprised of 600 bases, however, in reality the DNA sequence is longer than this.

What is the reason for this difference?

  • presence of introns and start/stop codons

  • presence of exons and start/stop codons

  • presence of introns

  • presence of exons

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61 mark

A polypeptide has the amino acid sequence alanine–valine–lysine–serine–glycine.

The table gives some possible tRNA anticodons for each amino acid.

amino acid tRNA anticodons

serine 

valine 

lysine 

alanine

glycine

UCG            UCA

GUA            GUC

   AAA             AAG   

GCU            GCG

GGA            GGC

Which sequence of bases on DNA could code for the polypeptide?

  • GCUGUCAAAGUAUGA

  • GCTGTCAAAAAGGAG

  • GCUGUAAAGUCGUAA

  • GCTGTAAAGTCGGGC

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71 mark

Which statements are correct about DNA replication, transcription and translation?

  DNA replication transcription translation
A produces mRNA occurs in the cytoplasm tRNA involved
B DNA polymerase involved RNA polymerase involved produces mRNA
C is semi-conservative produces mRNA occurs at a ribosome
D occurs in the nucleus occurs in the nucleus RNA polymerase involved

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    81 mark

    Which term best describes a section of DNA that codes for the synthesis of a polypeptide?

    • protein

    • gene

    • exon

    • triplet

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    91 mark

    Why does a silent mutation have no effect on the polypeptide chain?  

    • the dominant allele can compensate for the silent mutation

    • a silent mutation does not cause a frameshift

    • a silent mutation substitutes for a similar type of amino acid

    • multiple codons can code for the same amino acid

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    101 mark

    Which enzymes are not needed for DNA transcription?

    1 Helicase
    2 DNA ligase
    3 RNA polymerase
    4 DNA polymerase

    • 1, 2 and 3 only

    • 2 and 3 only

    • 2 and 4 only

    • 1 and 3 only

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    11 mark

    Ribosomes exist as two separate subunits that join together during protein synthesis.

    What do these subunits consist of?

    • rRNA and protein

    • rRNA and lipid

    • rRNA and mRNA

    • rRNA and tRNA

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    21 mark

    The diagram shows a section of DNA. 

    q22

    What would the corresponding anticodon sequence be for the third DNA triplet? 

    • G A T

    • C T A

    • C U G

    • G A U

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    31 mark

    The diagram shows two sections of RNA. 

    q23

    Which row of the table is correct?

      process X is needed to make a functional protein strand 1 is mRNA strand 2 is mRNA process X removes exons

    strand 1 contains introns and exons 
    A X ✓ X X ✓
    B ✓ X ✓ X ✓
    C X X ✓ ✓ ✓
    D ✓ ✓ ✓ X X

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      41 mark

      A polypeptide has the amino acid sequence:

      alanine – alanine – valine – lysine – valine – serine

      The table gives the DNA triplets for each amino acid.

      amino acid DNA triplets

      serine 

      valine 

      lysine

      alanine 

      stop

      TCG

      GTA

      AAA

      GCT

      TAA

      A substitution mutation in the DNA coding for this polypeptide chain caused the tenth nucleotide to swap from an A to a T

      How would the amino acid sequence in the polypeptide now look?

      • alanine – alanine – valine – lysine – valine – serine

      • alanine – alanine – valine – stop – valine – serine

      • alanine – alanine – valine 

      • alanine – alanine – valine – serine – valine – serine

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      51 mark

      Some antibiotics work by preventing protein synthesis in bacteria by binding to their ribosomes.

      Which statement explains why these antibiotics kill bacterial cells but not human cells?

      • ribosomes in human cells have a different structure to those in bacterial cells

      • antibiotics recognise human antigens on the cell membrane

      • both DNA and ribosomes are located in the cytoplasm in bacteria

      • bacterial cells have different nucleotides to human cells

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      61 mark

      Which of the following statements is not a description of a gene?

      • Any section of a double stranded DNA molecule with a sequence of complementary nucleotides held together by hydrogen bonding.

      • A sequence of nucleotides that can be transcribed using a polymerase enzyme and free activated nucleotides, which results in the formation of mRNA.

      • A length of DNA which carries coded information as a sequence of nucleotides that can result in the formation of a polypeptide chain.

      • A sequence of nucleotides which can be copied by complementary base pairing and then be translated at a ribosome.

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      71 mark

      Which row in the table correctly shows situations in which both DNA and RNA are involved?

        replication transcription translation protein synthesis
      A ✓ ✓ X X
      B ✓ X ✓ X
      C X X ✓ X
      D X ✓ X ✓

       key

      ✓  involved

       X not involved

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        81 mark

        A gene produces a pre-RNA that is 1450 bases in length and has the following intron-exon structure:

                  Exon 1 - 250 bp

                  Intron 1 - 150 bp

                  Exon 2 - 50 bp

                  Intron 2 - 250 bp

                  Exon 3 - 750 bp

        How many bases would the mRNA created from this gene have?

        • 400

        • 1050

        • 1250

        • 1400

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        91 mark

        In eukaryotes, which of the following statements is true with regards to introns and exons?

        • mature mRNA contains a mix of introns and exons

        • failure to remove introns can lead to production of faulty protein

        • exons in protein coding genes are removed by spliceosomes

        • exons are repeating sequences that are typically found at the end of a gene

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        101 mark

        A polypeptide has the amino acid sequence: 

        histidine – glutamine – lysine – alanine – valine – histidine – valine

        The table gives the tRNA anticodons for each amino acid.

        amino acid tRNA anticodons

        histidine

        valine 

        lysine 

        alanine 

        glutamine

        CAU

        GUA

        AAA

        GCU

        CAG

        A mutation causes the 18th base in the DNA sequence to be deleted.

        What would the amino acid sequence look like following this change? 

        • histidine – glutamine – lysine – alanine – valine – histidine

        • histidine – glutamine – lysine – alanine – valine

        • histidine – glutamine – lysine – alanine – valine – glutamine

        • histidine – glutamine – lysine – alanine – valine – histidine – valine

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