Scientists and Their Experiments

Flashcards reviewing key experiments and scientists involved in the discovery of DNA's structure and function.

Friedrich Miescher (1869)

Experiment: Isolated 'nuclein' from cell nuclei

Conclusion: Identifying a unique substance (DNA) but not realizing its hereditary role.

Fred Griffith (1928)

Experiment: Transformed Streptococcus pneumoniae strains in mice

Conclusion: Discovering a 'transforming factor' that could transfer genetic traits.

Joachim Hammerling (1943)

Experiment: Grafted Acetabularia algae parts

Conclusion: Nucleus contains information determining cell characteristics.

Phoebus Levene (1920s-1949)

Experiment: Analyzed DNA's components

Conclusion: Identifying deoxyribose sugars, phosphate groups, and nitrogenous bases (A, G, T, C) as DNA's building blocks.

Avery, MacLeod, & McCarty (1944)

Experiment: Griffith’s work- Used S and R strains of streptococcus bacteria to destroy DNA, RNA or proteins.

Conclusion: DNA is the "transforming factor" responsible for heredity.

Erwin Chargaff (1950)

Experiment: Separated DNA into individual components using paper chromatography, converted separated compounds into mercury salts. Identified purines/pyrimidines by their ultraviolet absence.
Conclusion: Established A=T and G=C, disproved tetranucleotide hypothesis.

Hershey & Chase (1952)

Experiment: Used bacteriophages to determine if DNA or protein was the gene material

Conclusion: DNA is the genetic material.

Rosalind Franklin & Maurice Wilkins (1952)

Experiment: Used X-ray crystallography to study DNA structure

Conclusion: Revealed DNA's helical structure. Sugar phosphate backbone, double helix, nitrogenous base pairing.

Watson & Crick (1953)

Built physical models of DNA, using Franklin’s X-ray data and Chargaff's rules.

Conclusion: DNA’s structure- antiparallel strands, sugar phosphate backbone, double helix, nitrogenous base pairing

Meselson & Stahl (1958)

Experiment: How DNA replicates using e.coli

Conclusion: Confirmed DNA replicated semi conservatively