Biology Experiment ✍🏻

 The Meselson-Stahl experiment! 

*The Meselson-Stahl Experiment (1958)*

The Meselson-Stahl experiment was a groundbreaking study conducted by Matthew Meselson and Franklin Stahl. It provided strong evidence for the semi-conservative replication model of DNA.

*Key Findings:*

1. *Experimental Design:*

    - They grew E. coli bacteria in a medium containing heavy nitrogen (¹⁵N) for many generations.

    - They then transferred the bacteria to a medium containing light nitrogen (¹⁴N) and allowed them to replicate.

2. *Density Gradient Centrifugation:*

    - They used density gradient centrifugation to separate DNA molecules based on their density, which is determined by their nitrogen content.

3. *Results:*

    - After one generation, they observed a single band of DNA with an intermediate density between ¹⁵N and ¹⁴N.

    - After two generations, they observed two bands: one with intermediate density and one with light density (¹⁴N).

*Conclusion:*

The Meselson-Stahl experiment demonstrated that DNA replication is semi-conservative, meaning that each new DNA molecule consists of one old strand (from the parent molecule) and one newly synthesized strand.

*Semi-Conservative Replication Model:*

1. The double helix is unwound, and the strands are separated.

2. Each strand serves as a template for the synthesis of a new complementary strand.

3. The resulting DNA molecules each contain one old strand and one new strand.

*Significance:*

The Meselson-Stahl experiment provided strong evidence for the semi-conservative replication model, which is a fundamental concept in molecular biology. It has had a lasting impact on our understanding of DNA replication and genetics.

*Next Question:*

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