Meselson-Stahl Experiment

Definition

The Meselson-Stahl experiment is a landmark study that provided strong evidence for the semi-conservative model of DNA replication, demonstrating that each new DNA molecule consists of one old strand and one newly synthesized strand. This experiment used isotopes of nitrogen to trace the incorporation of parental DNA into newly formed DNA during replication, establishing a clear understanding of how genetic information is copied in living organisms.

5 Must Know Facts For Your Next Test

1. The Meselson-Stahl experiment was conducted in 1958 by Matthew Meselson and Franklin Stahl at Caltech.
2. They grew E. coli bacteria in a medium containing heavy nitrogen (^15N) for several generations, allowing the bacteria's DNA to incorporate this heavier isotope.
3. After switching the bacteria to a lighter medium with normal nitrogen (^14N), they collected samples at different time points to observe the resulting DNA density.
4. The use of density gradient centrifugation allowed them to separate DNA molecules based on their density, revealing distinct bands that supported the semi-conservative model.
5. The results showed that after one round of replication, DNA had an intermediate density, indicating that each DNA molecule contained one strand of heavy DNA and one strand of light DNA.

Review Questions

• How did the design of the Meselson-Stahl experiment support the theory of semi-conservative replication?
  • The design of the Meselson-Stahl experiment involved growing E. coli in a medium with heavy nitrogen (^15N) and then transferring them to a lighter medium with normal nitrogen (^14N). By analyzing the density of the resulting DNA through centrifugation, they observed that after one round of replication, the DNA displayed an intermediate density. This indicated that each new DNA molecule consisted of one heavy strand from the parental DNA and one newly synthesized light strand, confirming the semi-conservative model.
• Discuss the significance of isotope labeling in tracing the process of DNA replication in the Meselson-Stahl experiment.
  • Isotope labeling was crucial in the Meselson-Stahl experiment as it enabled researchers to track the incorporation of nitrogen into DNA strands. By using heavy nitrogen (^15N), they could differentiate between old and new strands after replication. This clear distinction allowed them to visualize how parental DNA was retained in new molecules, thus providing strong evidence for the semi-conservative nature of DNA replication.
• Evaluate how the findings from the Meselson-Stahl experiment have influenced our understanding of genetic inheritance and molecular biology.
  • The findings from the Meselson-Stahl experiment fundamentally changed our understanding of genetic inheritance by confirming that DNA replication is semi-conservative. This revelation has vast implications for molecular biology, as it elucidates how genetic information is accurately transmitted from one generation to the next. Furthermore, it laid the groundwork for future research in genetics, molecular mechanisms, and biotechnology, impacting fields ranging from evolutionary biology to genetic engineering and therapeutic developments.

Related terms

Semi-conservative replication: The mechanism of DNA replication where each new double helix contains one original strand and one newly synthesized strand.

Isotope labeling: A technique that uses isotopes, such as heavy nitrogen, to trace biological processes or chemical reactions.

DNA centrifugation: A method used to separate molecules based on their density, which was crucial in the Meselson-Stahl experiment to analyze the DNA after replication.