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PUCET (Punjab) DNA Replication — practice questions

Explore 4 free DNA Replication questions in PUCET (Punjab) Biology. Open each question or exercise to read its content, reference answers and available explanation.

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DNA Replication questions and exercises with answers

Showing questions 1–4 of 4.

DNA replication is best described as:Read the answer and worked solution →The semiconservative nature of DNA replication was experimentally proved by:Read the answer and worked solution →**Okazaki fragments** on the lagging strand are joined together by the enzyme:Read the answer and worked solution →DNA polymerase synthesises new DNA strand in the:Read the answer and worked solution →

Worked practice questions

DNA replication is best described as:

  1. Conservative
  2. Dispersive
  3. Semiconservative
  4. Bidirectional only
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Correct answer: C. Semiconservative

Semiconservative — each daughter DNA has one **parental** strand and one **newly synthesised** strand. Proposed by Watson and Crick (1953) and proved experimentally by Meselson and Stahl (1958) using ¹⁵N/¹⁴N density gradient centrifugation.

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The semiconservative nature of DNA replication was experimentally proved by:

  1. Watson and Crick
  2. Meselson and Stahl (1958)
  3. Hershey and Chase
  4. Avery, MacLeod and McCarty
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Correct answer: B. Meselson and Stahl (1958)

Meselson and Stahl (1958) cultured *E. coli* on ¹⁵N medium, transferred to ¹⁴N, and used density-gradient centrifugation in CsCl. After one generation, a single intermediate-density band appeared (one heavy, one light strand) — confirming semiconservative replication.

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**Okazaki fragments** on the lagging strand are joined together by the enzyme:

  1. DNA polymerase I
  2. DNA polymerase III
  3. DNA ligase
  4. Helicase
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Correct answer: C. DNA ligase

DNA ligase seals the nicks (phosphodiester bonds) between adjacent Okazaki fragments after the RNA primers are removed and replaced with DNA. Polymerases extend strands helicase unwinds the parent duplex ligase joins.

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