History of Molecular Genetics (Kevin - Gr 12 Bio)

This set of cards outline notable scientists in history who made discoveries related to the field of molecular genetics, such as which molecule is used to transport genetic material and how genetic material is replicated.

Friedrich Miescher

Extracted a viscous white substance from the nucleus of a cell, which was rich in phosphorus and nitrogen. He named it nuclein. (it’s what we now know as DNA/RNA)

Frederick Griffith

Conducted the mice experiments (4 trials), using S-strains (deadly) and R-strains (safe). Discovered that living bacteria can uptake genetic material from dead bacteria in a process known as bacterial transformation.

Oswald Avery, Macly McCarty, and Colin McLeod

They induced rupture of heated dead S-strain S. pneumonia cells, and then removed certain biomolecules, to see if transformation would still occur. Transformation stopped when DNA is removed, therefore it requires DNA to occur. It could occur without RNA/protein.

Joachim Hammerling

In the one-celled green algae Acetabularia, genetic material is stored in the foot. When the foot is removed, it didn’t regenerate (because it lost the genetic material), but it did regenerate when only the head was removed.

Erwin Chargaff

Discovered that the amount of adenine and thymine are equal; and the amount of guanine and cytosine are equal. Also discovered that composition/ratio of nucleotides vary across species.

He used chromatography to separate DNA components, which he then analyzed through ultraviolet spectrophotometry.

Alfred Hershey & Martha Chase

Viruses inject DNA (not protein) into host cells.

Two trials

• Trial 1: sulfur (found only in viral protein) is made radioactive. Results: host cell is not radioactive, therefore viral protein did not enter host cell.

• Trial 2: phosphorus (found only in viral DNA) is made radioactive. Results: host cell is radioactive, therefore viral DNA did enter the host cell.

Rosalind Franklin & Raymond Gosling

The sugar-phosphate backbone lies outside of the DNA molecule, not inside.

DNA has two forms: wet (long & thin) and dry (short & fat).

James Watson & Francis Crick

Nucleotides make hydrogen bonds, creating a complementary double-helix structure that is antiparallel.

Matthew Methelson & Franklin Stahl

DNA replication is semi-conservative (1/2 of double helix is old, ½ is new).