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.