Q1. [3] deep thorough-understanding
A mutant pea plant produces an enzyme involved in growth-hormone synthesis, but that enzyme functions at only 20% of normal efficiency. Predict the likely appearance of this plant and justify your answer using the relationship between genes, enzymes, and traits.
Generated by claude-sonnet-4-6 · 2026-06-26 01:04 · grounding rag
Model Answer
The mutant plant will most likely appear shorter than normal (dwarf-like).
Justification: Genes control traits by producing specific enzymes. Here, the gene for growth-hormone synthesis produces an enzyme working at only 20% efficiency, meaning far less growth hormone is synthesised. Since adequate growth hormone is not available, the plant cannot achieve normal height. This demonstrates the direct gene → enzyme → trait relationship: a defective gene leads to a less functional enzyme, which alters the final observable trait (phenotype).
Explanation
- The key concept tested is gene → enzyme → trait: genes code for enzymes; enzymes drive biochemical reactions; reactions determine the trait.
- The examiner wants you to link reduced enzyme efficiency → reduced hormone production → altered phenotype in a logical chain.
- At 20% efficiency, growth hormone is severely limited, so the most predictable effect is stunted/reduced growth — draw this conclusion clearly.
- This question is application-based; the source passages establish that genes control traits (Chapter 8), so ground your answer in that principle even though the exact enzyme scenario isn't explicitly described.