Lac Operon & Gene Regulation — NEET Biology
✅ Asked in NEET 2024Match List I with List II: A. Frederick Griffith B. Francois Jacob and Jacques Monod C. Har Gobind Khorana D. Meselson and Stahl List II I. Genetic code II. Semi-conservative mode of DNA replication III. Transformation IV. Lac operon
Match List I with List II: A. Frederick Griffith B. Francois Jacob and Jacques Monod C. Har Gobind Khorana D. Meselson and Stahl List II I. Genetic code II. Semi-conservative mode of DNA replication III. Transformation IV. Lac operon
Select the correct match: (NEET 2018)
Answer & NCERT explanation
Correct answer: B — A-III, B-IV, C-I, D-II
Correct matching according to NCERT: Frederick Griffith discovered transformation using Streptococcus pneumoniae; Jacob & Monod proposed lac operon model; Har Gobind Khorana deciphered the genetic code; Meselson & Stahl proved semiconservative DNA replication. This gives A-III, B-IV, C-I, D-II which matches option (b). All other combinations incorrectly pair scientists with their discoveries.
Read more NCERT concept on the PYQ
The elucidation of the lac operon was also a result of a close association between a geneticist, Francois Jacob and a biochemist, Jacque Monod. They were the first to elucidate a transcriptionally regulated system. In lac operon (here lac refers to lactose), a polycistronic structural gene is regulated by a common promoter and regulatory genes. Such arrangement is very common in bacteria and is referred to as operon. To name few such examples, lac operon, trp operon, ara operon, his operon, val operon, etc.
The lac operon is a polycistronic transcriptional unit discovered by Jacob and Monod, showing how bacteria regulate genes using promoters and regulatory genes. NTA tests whether students understand that operons contain multiple structural genes under one promoter, and that this is a bacterial adaptation for coordinated gene expression. Students often confuse operons with individual genes or assume eukaryotes use operons similarly—they don't. Remember: operons are bacterial clusters of functionally related genes controlled together; Jacob-Monod proved this experimentally, which revolutionized understanding of gene regulation. This concept appears frequently because it bridges genetics with molecular biology and asks students to apply regulatory principles.
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Through deep analysis of NEET and NTA, 88 of 90 questions from the NEET 2026 paper were matched straight from the MedicNEET Biology question bank.
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