History of Genetics and the Discovery of DNA

Vocabulary practice flashcards covering the key scientists, experiments, and milestones in the history of genetics and the discovery of DNA structure.

Gregor Mendel

Known as the Father of Genetics (1865) who worked with pea plants in a monastery and founded genetics concepts including the Punnett Square, Dominant vs Recessive traits, Dihybrid Cross, Law of Segregation, and Law of Independent Assortment.

Friedrich Miescher

A Swiss chemist working in Germany who, in 1869, was the first to isolate nucleic acids from cell nuclei.

Nuclein

The name originally given by Friedrich Miescher to the substance isolated from cell nuclei, determined to consist of an acidic portion (nucleic acid) and an alkaline portion (later shown to be a protein).

Thomas Hunt Morgan

Scientist who conducted experimental work in the early 1900's with fruit flies (Drosophila melanogaster), establishing that genes were the unit of heredity arranged linearly on chromosomes like beads on a necklace.

Phoebus Levene

Biochemist (1900-1930's) who isolated DNA and RNA, identified the nucleotide, discovered minor bases, and incorrectly thought nucleic acids consisted of equal parts of repeating strands of nucleotides.

Nucleotide

A subunit discovered by Phoebus Levene composed of a sugar, a phosphate group, and a nitrogenous base: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T) or Uracil (U) in RNA.

Frederick Griffith

Scientist who worked in 1928 with two strains of pneumonia-causing bacteria, discovering that living bacteria could take up genetic information from dead pathogenic cells and deducing that protein was not the hereditary material.

Transformation

The process discovered by Frederick Griffith in 1928 where bacteria take up genetic information from their environment, allowing dead cells' pathogenic properties to be passed on to living cells.

Joachim Hammerling

Researcher in the 1930's who used the single-celled algae Acetabularia to determine that genetic and hereditary information is located in the nucleus at the foot of the cell.

Acetabularia

A single-celled algae with a nucleus near the base (called the foot) and a stalk leading to a cap, used by Joachim Hammerling to study the cellular location of hereditary material.

Avery, McLeod and McCarty

Researchers who in 1944 identified Griffith's transforming material as DNA, discovering that somatic cells contain double the quantity of DNA compared to gametes and that each somatic cell within an organism has the same quantity of DNA.

Erwin Chargaff

Scientist who in 1949 proved Phoebus Levene wrong by discovering that the 4 nucleotides are not present in equal quantities but in characteristic proportions, which remain constant across different animals of the same species regardless of age, physical state, or environment.

Chargaff Rule

The rule formulated by Erwin Chargaff stating that in DNA, the amount of adenine equals thymine ($A = T$) and the amount of cytosine equals guanine ($C = G$).

Alfred Hershey & Martha Chase

Researchers who in 1952 used their famous blender experiment to provide evidence that DNA, rather than protein, is the carrier of genetic information.

Linus Pauling

A researcher at the University of California who was one of the three competing teams racing to uncover the physical structure of DNA.

Rosalind Franklin & Maurice Wilkins

Researchers at King's College, London, who used X-ray diffraction on crystalline DNA to reveal a helical structure featuring hydrophobic nitrogenous bases on the inside and a sugar-phosphate backbone on the outside.

James Watson & Francis Crick

Scientists at the Cavendish Lab at Cambridge University who in 1953 built the physical model of DNA as a double helix with complementary base pairing ($A$ with $T$, and $C$ with $G$), utilizing the work of Chargaff, Franklin, and Wilkins to win the Nobel Prize.