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Ch. 11 - DNA Replication and Recombination
Klug - Concepts of Genetics  12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
Chapter 11, Problem 3

Compare conservative, semiconservative, and dispersive modes of DNA replication.

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Step 1: Define each mode of DNA replication clearly. Conservative replication means the original DNA molecule remains intact, and an entirely new copy is made, resulting in one completely old and one completely new DNA molecule.
Step 2: Explain semiconservative replication, where each of the two new DNA molecules consists of one original (parental) strand and one newly synthesized strand.
Step 3: Describe dispersive replication, in which the original DNA strands are broken into pieces, and the new DNA molecules are a mix of old and new DNA segments interspersed along each strand.
Step 4: Compare the outcomes of each mode in terms of the composition of the daughter DNA molecules after one round of replication, focusing on how parental and new strands are distributed.
Step 5: Discuss experimental evidence (such as the Meselson-Stahl experiment) that supports semiconservative replication as the actual mechanism in cells, highlighting why the other models were ruled out.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Conservative DNA Replication

In conservative replication, the original DNA molecule remains intact, and an entirely new copy is synthesized. After replication, one daughter molecule contains both original strands, while the other contains two new strands. This model was an early hypothesis but was later disproven by experimental evidence.
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Semiconservative DNA Replication

Semiconservative replication involves each of the two original DNA strands serving as a template for a new strand. After replication, each daughter DNA molecule consists of one original strand and one newly synthesized strand. This model is supported by experimental data and is the accepted mechanism in cells.
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Dispersive DNA Replication

Dispersive replication proposes that the original DNA strands are broken into segments, and new DNA is synthesized in short fragments interspersed with old DNA. The resulting daughter molecules are mixtures of old and new DNA along each strand. This model was also disproven by experiments.
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