1. 11/07/08
Lecture 26 – Molecular Genetics 1
 History of Genetics (DNA)
 1869 – Fredrick Meischer
 Swiss biochemist
 Looked at cells (pus cells and salmon sperm)
 Isolated nuclein (DNA)
 1800's → 1900's
 Search for hereditary material
 Features of heredity (Cells/DNA)
 Able to replicate
 Able to store large amounts of information
 Able to read information
 Chromosome (protein and DNA) were biochemically analyzed
 1928 – Frederick Griffith
 Researched the bacterium, streptococcus pneumoniae.
 Caused pneumonia in mice
 2 stains in bacteria
 S-strain (smooth)
 virulent strain
 R-strain (rough)
 Conclusion: somehow the R-strain transformed into the S-strain
 Postulate a transforming factor.
 1944 – Avery, McLeod and McCarty
 Instead of heat-killed smooth → they just used DNA
 R-strain –transformed→ S-strain (transforming factor is DNA)
 1950 – Erwin Chargaff
 Discovered the amount of adenine always equaled the amount of thymine, guanine equaled cytosine
 1953 – James Watson and Crick Cambridge V.
 Published the model of DNA
 DNA (RNA)
 Composed of units (nucleotides).
 Nucleotides polymerize to form nucleotides chains.
 Nucleotides consist of a phosphate group, 5-carbon sugar and nitrogen base.
 DNA is composed of adenine, thymine, guanine, and cytosine.
 RNA contains the same nucleotides but thymine is replaced with uracil.
 In DNA, there are two strands in opposite directions (anti-parallel) coiled into a double helix.
 Functioning of DNA and RNA in the cell
 Sometimes known as the “central dogma of the molecular biology”.
 Replicates
 DNA codes for proteins.
 Replication: The process of cellular devision by duplicating DNA.
 Transcription: The process whereby the DNA sequence in a gene is copied into mRNA
 Translation: The process of using mRNA to form a specific protein.