A Levels Biology (9700)•9700/13/M/J/25

Explanation
Genes match distinct polypeptide subunits in proteins
Steps:
- Determine protein structure: count unique subunits for each protein.
- Protein 1: trimeric with three different chains requires 3 genes.
- Protein 2: heterodimeric with two different chains requires 2 genes.
- Protein 3: monomeric with one chain requires 1 gene.
- Match to row: 3 2 1.
Why C is correct:
- Matches the one gene per unique polypeptide rule in eukaryotic protein synthesis.
Why the others are wrong:
- A: Undercounts complex protein (1 instead of 3 genes).
- B: Overcounts dimer (4 instead of 2 genes).
- D: Overcounts monomer (2 instead of 1 gene).
Final answer: C
Topic: Protein synthesis
Practice more A Levels Biology (9700) questions on mMCQ.me