Match the experiment with the conclusion derived from that experiment Griffith Experiment [Choose] Hershey & Chase Experiment [Choose] Meselson & Stale Experiment [Choose]
The Correct Answer and Explanation is:
Correct Matches:
- Griffith Experiment → Something in heat-killed bacteria can transform live bacteria
- Hershey & Chase Experiment → DNA is the genetic material
- Meselson & Stahl Experiment → DNA replicates semi-conservatively
Explanation (Approximately 300 words, no em dashes):
Each of these classic experiments played a vital role in uncovering the nature and behavior of genetic material.
Griffith’s Experiment (1928):
Frederick Griffith worked with two strains of Streptococcus pneumoniae: a virulent smooth (S) strain and a non-virulent rough (R) strain. He found that when he injected mice with heat-killed S strain and live R strain together, the mice died. Moreover, live S strain bacteria were recovered from the dead mice. This indicated that some “transforming principle” from the dead S bacteria had turned the harmless R strain into a harmful form. Although the exact substance was unknown at the time, this experiment suggested that genetic information could be transferred between organisms.
Hershey & Chase Experiment (1952):
Alfred Hershey and Martha Chase used viruses called bacteriophages, which infect bacteria. They labeled the DNA of the viruses with radioactive phosphorus (P-32) and the protein coat with radioactive sulfur (S-35). After allowing the viruses to infect bacteria, they used a blender and centrifuge to separate the viral protein coats from the bacteria. Only the radioactive phosphorus entered the bacterial cells, showing that DNA—not protein—carried the genetic instructions. This experiment confirmed that DNA is the genetic material.
Meselson & Stahl Experiment (1958):
Matthew Meselson and Franklin Stahl grew E. coli bacteria in a medium containing heavy nitrogen (N-15) and then transferred them to a medium with normal nitrogen (N-14). After each generation, they extracted DNA and used density gradient centrifugation to analyze it. The first generation produced DNA of intermediate density, and later generations showed both light and intermediate densities. This proved that DNA replication is semi-conservative: each new DNA molecule consists of one old strand and one newly synthesized strand.
These experiments collectively transformed our understanding of heredity, confirming that DNA is the molecule of inheritance and explaining how it replicates.
