Understanding the Meselson-Stahl Experiment

Mr. Anderson explains the Meselson-Stahl experiment, which determined the method of DNA replication. After Watson and Crick proposed the double helix structure, three replication theories emerged: semiconservative, conservative, and dispersive. The experiment used E. coli grown in heavy nitrogen to track DNA replication. Results showed DNA replication is semiconservative, where each new DNA molecule consists of one old and one new strand. This experiment was crucial in understanding DNA replication.

What was the main focus of the Meselson-Stahl experiment?

• To determine the structure of DNA

• To identify the method of DNA replication

• To discover new elements in DNA

• To study the effects of radiation on DNA

Which of the following was NOT a proposed model for DNA replication?

• Recombinant model

• Dispersive model

• Conservative model

• Semiconservative model

What is the significance of using heavy nitrogen in the experiment?

• It prevents DNA from replicating

• It makes DNA replication faster

• It allows differentiation between old and new DNA strands

• It changes the color of DNA

How does heavy nitrogen affect the DNA in the centrifuge?

• It changes the DNA color

• It makes DNA sink to the bottom

• It breaks the DNA into pieces

• It causes DNA to float

What happens to the DNA strands after the first replication in lighter nitrogen?

• They become completely light

• They remain completely heavy

• They form hybrid strands

• They disintegrate

In the semiconservative model, what percentage of DNA is hybrid after the second replication?

• 75%

• 100%

• 25%

• 50%

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

• It is dispersive

• It is random

• It is conservative

• It is semiconservative

Why is the Meselson-Stahl experiment considered elegant?

• It used complex machinery

• It was conducted over a long period

• It provided a simple yet effective method to understand DNA replication

• It involved multiple organisms

What was the role of Martha Chase in the context of the experiment?

• She conducted the centrifuge process

• She was part of the Hershey-Chase experiment

• She proposed the semiconservative model

• She discovered heavy nitrogen

What does the semiconservative model of DNA replication imply?

• DNA strands are completely new after replication

• Each new DNA molecule consists of one old and one new strand

• DNA strands are mixed randomly

• DNA strands do not replicate