Q.91 The relationship between genes and enzymes was first suggested by the discovery of
(A) in-born errors of metabolism in human
(B) sexual phenotype in insects
(C) metabolic pathways in fungi
(D) gene regulation in bacteria
The one gene-one enzyme hypothesis linking genes directly to enzymes originated from Archibald Garrod’s 1908 study of inborn errors of metabolism in humans, like alkaptonuria, where genetic defects caused enzyme deficiencies.
Beadle and Tatum later confirmed this experimentally in Neurospora, but Garrod first suggested the relationship.
Correct Answer
(A) in-born errors of metabolism in human
Option Analysis
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(A) in-born errors of metabolism in human: Garrod observed inherited disorders (e.g., alkaptonuria due to homogentisate oxidase defect) where single gene mutations blocked specific metabolic steps, first proposing “inborn errors” where genes dictate enzymes. This 1908 insight predates experimental genetics.
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(B) sexual phenotype in insects: Sex determination in insects (e.g., Drosophila Sxl gene) involves cascades but doesn’t establish gene-enzyme links; phenotypes relate more to regulatory genes than metabolic enzymes.
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(C) metabolic pathways in fungi: Beadle-Tatum’s 1941 Neurospora work mapped mutations to enzyme blocks in pathways (e.g., arginine synthesis), confirming Garrod’s idea via “one gene-one enzyme” but not the first suggestion.
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(D) gene regulation in bacteria: Lac operon (Jacob-Monod, 1961) showed regulatory genes controlling enzymes but focused on induction/repression, not the foundational gene-enzyme correspondence.
Historical Context
Garrod linked inherited traits to biochemical defects: normal → gene → enzyme → metabolite. Alkaptonuria mutants accumulated homogentisic acid due to enzyme absence, suggesting genes code for enzymes. This inspired Beadle-Tatum’s systematic Neurospora auxotrophs.
Genes Enzymes Relationship In-Born Errors: First Discovery
The genes enzymes relationship in-born errors concept began with Garrod’s human metabolic disorders. In 1908, he proposed genes specify enzymes, using alkaptonuria as evidence where enzyme defects cause metabolite buildup.
Discoveries Compared
| Discovery | Key Scientist(s) | Contribution to Gene-Enzyme Link |
|---|---|---|
| In-born errors | Garrod (1908) | First suggestion: genes → enzymes |
| Sexual phenotype insects | Bridges et al. | Dosage compensation, not enzymes |
| Fungi pathways | Beadle-Tatum (1941) | Experimental confirmation |
| Bacteria regulation | Jacob-Monod (1961) | Control mechanisms |
Genes enzymes relationship in-born errors laid biochemical genetics foundation, essential for GATE Life Sciences. Beadle-Tatum Nobel (1958) validated Garrod’s vision.
GATE Prep Insights
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Garrod’s examples: Alkaptonuria, albinism, cystinuria.
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Principle: Mutation → enzyme loss → pathway block → phenotype.
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Test focus: Historical priority over later confirmations.
