Question

Describe Meselson-Stahl experiment and explain how it showed that DNA replication is semiconservative?

A. Meselson-Stahl used radioisotopes to label newly synthesized DNA strands, confirming semiconservative replication.
B. Meselson-Stahl observed DNA denaturation, proving semiconservative replication.
C. Meselson-Stahl discovered DNA helicase, supporting semiconservative replication.
D. Meselson-Stahl studied DNA ligase, confirming semiconservative replication.

Answer 1

The Meselson-Stahl experiment confirmed semiconservative DNA replication by using isotopes of nitrogen to track the incorporation into DNA and observing the densities of the resulting DNA after ultracentrifugation.

Step-by-step explanation:

The Meselson-Stahl experiment from 1958 demonstrated how DNA replication is semiconservative. By growing E. coli in a medium with a heavy isotope of nitrogen (15N) and then transferring them to a medium containing the lighter isotope (14N), they were able to show, through ultracentrifugation, that after one generation of growth in 14N, the isolated DNA formed a single band at an intermediate density, suggesting a semiconservative or dispersive replication model.

However, after allowing cells to grow for a second generation in 14N, two bands were observed: one at the intermediate position and one at the 14N density. This outcome confirmed that semiconservative replication occurs, as each new DNA molecule consists of one original parental strand and one newly synthesized complementary strand.