Question

What evidence convinced investigators that the original unlabeled DNA in the reaction mixture served as the template for the newly made DNA?

a. The new DNA had the same base composition as the original DNA.
b. The new DNA had a variable base composition.
c. The new DNA had a triple helix.
d. The new DNA and the old DNA were made of the same elements.
e. The new DNA was equally stable.

Answer 1

Matthew Meselson and Franklin Stahl's experiments showed that new DNA formed with an intermediate density after one generation, and with two distinct bands after two generations, confirming the semi-conservative model of DNA replication.

Step-by-step explanation:

The evidence that convinced investigators that the original unlabeled DNA served as the template for newly made DNA is best represented by the experiments of Matthew Meselson and Franklin Stahl. They observed that after one generation, the DNA in Escherichia coli had an intermediate density between DNA with only ^15N (heavier) and DNA with only ^14N (lighter), indicating that new DNA strands were synthesized using the original DNA strands as templates. This result was consistent with the semi-conservative model of DNA replication.

In their experiment, after two generations, the resulting DNA had one band at the intermediate position and another corresponding to the lighter ^14N DNA. This could only happen if one of the original strands is conserved in each of the new DNA molecules, firmly supporting the semi-conservative replication model.