Replication — NEET Biology Questions

Practice 52 questions on Replication from Molecular Basis of Inheritance (NCERT Class 12, Chapter 5). Free samples below — get all 52 in the app.

52 Questions Molecular Basis of Inheritance Class 12

Sample Questions — Replication

Try 5 questions below from Replication. Get all 52 in the MedicNEET app.

MCQ
15. What was the key finding from Meselson and Stahl’s experiment after two generations?
  • A. Only hybrid DNA present
  • B. Only light DNA present
  • C. DNA was radioactive
  • D. Both hybrid and light DNA present
✅ Correct Answer: D
This result confirms semiconservative nature of DNA replication.
MCQ
17. The enzyme required to seal gaps between Okazaki fragments is:
  • A. Helicase
  • B. DNA ligase
  • C. Primase
  • D. Gyrase
✅ Correct Answer: B
DNA ligase joins the sugar-phosphate backbone to seal nicks.
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MCQ
5. What is the role of the template strand during replication?
  • A. It degrades RNA
  • B. It provides energy
  • C. It guides the complementary strand
  • D. It initiates protein synthesis
✅ Correct Answer: C
The parental strand acts as a template to build a new strand.
MCQ
17. Why did the density of DNA decrease in the second generation?
  • A. DNA degraded
  • B. New strands were heavier
  • C. DNA had more purines
  • D. New strands were made with ¹⁴N
✅ Correct Answer: D
DNA synthesized after transferring to 14N medium becomes lighter.
MCQ
2. Match the following: Column I (Event) A. ¹⁵N incorporation B. Transfer to ¹⁴N mediumC. One generation after transfer D. Two generations after transfer Column II (Description) I. Intermediate density DNA II. Equal light and hybrid DNA III. Heavy DNA formation IV. Initiates hybrid DNA formation
  • A. A–I, B–II, C–III, D–IV
  • B. A–II, B–I, C–III, D–IV
  • C. A–III, B–IV, C–I, D–II
  • D. A–IV, B–III, C–II, D–I
✅ Correct Answer: C
When E. coli is grown in a medium containing heavy nitrogen (¹⁵N), its DNA becomes denser (“heavy DNA”). When these cells are shifted to a medium containing light nitrogen (¹⁴N), newly synthesized DNA strands incorporate ¹⁴N, producing hybrid (¹⁵N–¹⁴N) DNA after one generation. After two generations, half the DNA is hybrid and half is completely light (¹⁴N–¹⁴N), confirming the semiconservative mode of replication.

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