How were scientists able to determine that DNA, and not some other molecule, serves as the genetic material in bacteria and bacteriophages?

Verified step by step guidance

1. Understand the historical context: Scientists initially considered proteins as the genetic material because of their complexity and diversity, while DNA was thought to be too simple.
2. Examine the key experiment by Avery, MacLeod, and McCarty, who used purified components from heat-killed bacteria to transform non-virulent bacteria into virulent forms, showing that DNA was responsible for transformation.
3. Analyze the Hershey-Chase experiment, where bacteriophages were labeled with radioactive isotopes—phosphorus-32 to label DNA and sulfur-35 to label proteins—to track which molecule entered bacterial cells during infection.
4. Interpret the results of the Hershey-Chase experiment: the radioactive phosphorus (DNA) was found inside the bacteria, while the radioactive sulfur (protein) remained outside, indicating DNA carries genetic information.
5. Conclude that these experiments collectively demonstrated that DNA, not protein or other molecules, serves as the genetic material in bacteria and bacteriophages.

Key Concepts

Hershey-Chase Experiment

This pivotal experiment used bacteriophages labeled with radioactive isotopes to distinguish DNA from protein. By tracking which molecule entered bacterial cells during infection, scientists demonstrated that DNA, not protein, carried genetic information.

Role of Bacteriophages in Genetic Studies

Bacteriophages are viruses that infect bacteria, making them ideal for studying genetic material transfer. Their simple structure, composed mainly of DNA and protein, allowed researchers to isolate and test the function of each component in heredity.

Chemical Composition and Function of DNA

DNA is composed of nucleotides forming a stable, information-rich molecule capable of replication and encoding genetic instructions. Its unique properties, unlike proteins, made it a strong candidate for the genetic material before experimental confirmation.