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CAIE A-Level Biology 6.2 Protein Synthesis Question Bank

Practise protein-synthesis questions by tracing transcription and translation, using codons or anticodons and predicting mutation effects on polypeptides.

Syllabus
2028–2030
Course
Biology 9700
Level
AS

Exam points

  • use codon tables to link DNA triplets, mRNA codons, tRNA anticodons and amino acids
  • sequence transcription and translation roles for RNA polymerase, ribosomes and tRNA
  • predict substitution, deletion, insertion or mRNA cleavage effects on polypeptides

Covered syllabus points

6.2.1—Gene6.2.2—Universal genetic code and codons6.2.3—Transcription and translation roles6.2.4—DNA strands in transcription6.2.5—Post-transcriptional modification6.2.6—Gene mutations6.2.7—Types of mutations6.2.8—Effects on polypeptide produced

6.2 Protein Synthesis question 1

[Maximum number: 4]

Smooth muscle is a tissue composed of smooth muscle cells. The cells contain cytoplasm packed with proteins that are involved in contraction and relaxation.

Question (a)

(a)

Caldesmon is a large protein with a number of binding sites to attach to other proteins.

Caldesmon exists in two different forms, H-caldesmon and L-caldesmon.
H-caldesmon helps to regulate contraction and relaxation in smooth muscle cells.
L -caldesmon is found in some non-muscle cells, where it also acts as a regulatory protein.
- Caldesmon is coded for by a gene known as CALD1.
- CALD1 has 17 exons.
- The primary structure of H-caldesmon has a repeating sequence in the middle of the amino acid chain that is not present in L-caldesmon.

[ 4 ]

Question (i)

(i)

Researchers have discovered that a gene mutation is not the cause of the two different forms of caldesmon.

Explain what is meant by a gene mutation.

[ 2 ]

Question (ii)

(ii)

Researchers now know that the two different forms of caldesmon are the result of events occurring directly after transcription of DNA. Changes occur to the primary transcript that is formed by DNA transcription.

Suggest how the smooth muscle cells and non-muscle cells can produce different forms of caldesmon from the same primary transcript.

[ 2 ]
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