Question

frederick griffith (1928)

oswald avery (1944)

hershey and chase (1952)

erwin chargaff (1947)

Explanation:

• Frederick Griffith (1928): Conducted experiments with Streptococcus pneumoniae, discovering the "transforming principle" (suggesting genetic material could be transferred between bacteria).
• Oswald Avery (1944): Extended Griffith's work, showing that DNA (not protein) was the transforming principle by purifying and testing cell components.
• Hershey and Chase (1952): Used bacteriophages (viruses that infect bacteria) with radioactive labels to confirm DNA is the genetic material (DNA entered bacteria, not protein).
• Erwin Chargaff (1947): Discovered "Chargaff's rules": in DNA, the amount of adenine (A) equals thymine (T), and guanine (G) equals cytosine (C); A+G = T+C.

Answer:

Frederick Griffith (1928): Discovered the "transforming principle" in bacteria (suggesting genetic material transfer).
Oswald Avery (1944): Identified DNA as the transforming principle (not protein).
Hershey and Chase (1952): Confirmed DNA is the genetic material via bacteriophage experiments.
Erwin Chargaff (1947): Established Chargaff’s rules (A=T, G=C; A+G=T+C in DNA).