The Molecular Basis Of Inheritance

The Molecular Basis of Inheritance Scientist

Year of Experiment

Johannes Friedrich Meischer

1869

Phoebus Levene

Frederick Griffith

Oswald Avery, Colin MacLeod, & Maclyn McCarty

Alfred Hershey & Martha Chase

1909 and 1929

1927

1944

1952

Brief Description

Conclusion/Contribution

Isolated various phosphaterich chemicals (nucleic acids) from the nuclei of white blood cells

Paved the way for the identification of DNA as the molecule of inheritance

Studied structure and function of nucleic acids and characterized DNA and RNA. Found the structure of nucleotides and the composition of nucleic acids.

Discovered ribose in 1909 and deoxyribose in 1929; helped scientists understand how DNA was structured to pass on hereditary material.

Performed experiments with several strains of bacteria to understand virulent and nonvirulent types. Separated carbohydrates, lipids, proteins, DNA, and RNA from heat-killed virulent bacteria and added each to separate living, non-virulent bacteria. After culturing the bacteria, they found out that those exposed to DNA became virulent, while the others remained unchanged. They tagged bacteriophages with radioactive isotopes 32P and 35S. The phosphorus would label the DNA, while the sulfur would label the protein coat. When bacteria were infected with phage viruses, the phosphorus would always enter, but the sulfur stayed outside.

The living R bacteria had transformed into virulent S bacteria by an unknown, heritable factor from the dead S cells.

This research proved that DNA was the agent that carried the genetic characteristics from the virulent dead bacteria to the living non-virulent bacteria. DNA was the genetic material.

DNA from the viral nucleus, not protein from the viral coat, was infecting bacteria and producing thousands of progeny.

DNA composition varies in species, and there is equivalence in the number of A and T bases; and G and C bases. Formulated Chargaff ’s rules.

Erwin Chargaff

1947

Analyzed the base composition of DNA from various organisms.

Linus Pauling

1950s

Focused on discovering the three-dimensional structure of DNA.

Contributed toward discovering the structure of the DNA molecule

Maurice Wilkins & Rosalind Franklin

1950s

Used X-ray diffraction to formulate images of DNA, which Watson and Crick used

Contributed toward discovering the structure of the DNA molecule

to create their model

James Watson & Francis Crick

1953

Matthew Meselson & Franklin Stahl

1957

Kornberg & Kornberg

1950s

Built an accurate model of a DNA molecule, suggesting a double helix

Discovered the accurate structure of the DNA molecule

Used the Escherichia coli grown in the presence of the nitrogen isotope nitrogen-15, which was then switched to be grown with normal nitrogen, nitrogen-14.

Proved that DNA replicates semi-conservatively

Studied the synthesis of DNA and nucleic acids which control heredity

Discovery of "the mechanisms in the biological synthesis of deoxyribonucleic acid (DNA)