(A) P-3-i, Q-1-ii, R-2-iii, S-3-iv

(B) P-3-ii, Q-1-iii, R-2-iv, S-3-i

(C) P-2-ii, Q-1-iii, R-3-iv, S-1-i

(D) P-1-ii, Q-2-iii, R-3-i, S-3-iv

Introduction

Reporter genes are essential tools in plant transformation experiments. They help scientists confirm successful gene transfer and study gene expression. Each reporter gene originates from a specific organism and is detected using a particular assay system such as fluorescence, luminescence, fluorometric, or radioactive assays.

In this article, we will correctly match commonly used reporter genes with their source of gene and detection/assay system, followed by a detailed explanation of each option.

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Correct Answer

✅ Option (B)

P-3-ii, Q-1-iii, R-2-iv, S-3-i

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Detailed Explanation of Each Reporter Gene

P. β-glucuronidase (GUS)

• Source: E. coli (3)

• Detection: Fluorimetric assay (ii)

• Explanation:
  GUS is one of the most widely used reporter genes in plant molecular biology. It catalyzes reactions producing fluorescent compounds that are easily measured using fluorometric methods.

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Q. Green Fluorescent Protein (GFP)

• Source: Aequorea victoria (1)

• Detection: Fluorescence (iii)

• Explanation:
  GFP emits green light when excited by blue or UV light. Since it does not require any substrate, it allows real-time visualization of gene expression in living cells.

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R. Luciferase

• Source: Photinus pyralis (2)

• Detection: Luminescence (iv)

• Explanation:
  Luciferase produces light as a result of a biochemical reaction with luciferin. The emitted light is measured as luminescence, making it highly sensitive.

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S. Chloramphenicol Acetyl Transferase (CAT)

• Source: E. coli (3)

• Detection: Radioactive assay (i)

• Explanation:
  CAT activity is traditionally measured using radioactive substrates, making it one of the earliest reporter systems used in gene expression studies.

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Option-wise Analysis

Option (A)

❌ Incorrect

• Luciferase is wrongly matched with fluorescence instead of luminescence.

Option (B)

✅ Correct

• All reporter genes are correctly matched with their source and detection systems.

Option (C)

❌ Incorrect

• β-glucuronidase is incorrectly linked to Photinus pyralis.

• CAT detection is incorrectly assigned.

Option (D)

❌ Incorrect

• β-glucuronidase source is wrong.

• CAT detection system is mismatched.

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Conclusion

Understanding reporter genes, their origin, and detection methods is crucial for plant biotechnology and genetic engineering. Among the given options, Option (B) correctly matches all reporter genes with their respective sources and detection systems.

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Final Answer

✅ Option (B): P-3-ii, Q-1-iii, R-2-iv, S-3-i