Meselson-Stahl Experiment

The podcast discusses the Meselson-Stahl experiment, which confirmed the semi-conservative model of DNA replication. After Watson and Crick's discovery of the DNA double helix, three replication models were proposed: semi-conservative, conservative, and dispersive. Meselson and Stahl used E. coli grown in heavy nitrogen to determine the correct model. Their experiment showed that DNA replication involves splitting the DNA in half and adding new strands, supporting the semi-conservative model.

Which of the following was NOT a proposed model for DNA replication after the discovery of the double helix?

• Semi-conservative model

• Conservative model

• Dispersive model

• Recombinant model

What was the purpose of using heavy nitrogen in the Meselson-Stahl experiment?

• To differentiate between old and new DNA strands

• To prevent DNA from replicating

• To make the DNA strands visible under a microscope

• To increase the replication speed of DNA

How did Meselson and Stahl separate DNA strands based on their nitrogen content?

• By using a chemical reaction

• By using a spectrophotometer

• By using a microscope

• By using an ultracentrifuge

What was the composition of DNA strands after the first replication in lighter nitrogen?

• 100% heavy nitrogen

• 100% light nitrogen

• 50% heavy and 50% light nitrogen

• 75% heavy and 25% light nitrogen

What did the Meselson-Stahl experiment ultimately demonstrate about DNA replication?

• DNA replicates conservatively

• DNA replicates dispersively

• DNA replicates semi-conservatively

• DNA does not replicate