1.1 Overview and History
What is Molecular Biology?
Molecular biology is the branch of biology that studies the molecular basis of biological activity. It focuses on the interactions between various systems of a cell, including the interrelationship between DNA, RNA, and protein synthesis.
"The goal of molecular biology is to understand how the genes that make up chromosomes direct the synthesis of proteins, and how these proteins interact to form a complete living organism."
— James Watson
Historical Development
The Discovery of DNA (1869-1944)
- 1869 - Friedrich Miescher: Isolated "nuclein" from white blood cells, the first identification of DNA
- 1928 - Frederick Griffith: Discovered bacterial transformation, showing genetic material could be transferred
- 1944 - Avery, MacLeod, McCarty: Proved DNA is the "transforming principle" carrying genetic information
The Structure Era (1950-1960)
- 1950 - Erwin Chargaff: Discovered base pairing rules (A=T, G=C)
- 1952 - Hershey-Chase: Confirmed DNA as genetic material using bacteriophages
- 1953 - Watson & Crick: Proposed the double helix structure using Rosalind Franklin's X-ray data
- 1958 - Meselson-Stahl: Demonstrated semi-conservative DNA replication
The Genetic Code (1961-1967)
- 1961 - Nirenberg & Matthaei: Deciphered first codon (UUU = Phenylalanine)
- 1961 - Jacob & Monod: Proposed the operon model of gene regulation
- 1966 - Khorana: Synthesized genes and completed the genetic code
The Central Dogma
Francis Crick proposed the Central Dogma in 1958, which describes the flow of genetic information:
DNA → DNA
DNA → RNA
RNA → Protein
Note: Exceptions exist: reverse transcriptase can copy RNA → DNA (retroviruses), and RNA can replicate itself (RNA viruses). Prions represent another exception where proteins can influence the conformation of other proteins.
Model Organisms
Gene regulation, protein expression
Cell cycle, eukaryotic genetics
Development, apoptosis
Classical genetics, development
Mammalian disease models
Plant molecular biology