The History of DNA.  Chapter Eleven . Pages 243-250.

Four Characteristics of the Hereditary Material

1. Storage of information

2. Replication

3. Expression of the information

4. Variation and evolution over time( change or mutation  )

The Central Dogma

 DNA                        DNA                      mRNA                   Protein

Replication                                             protein synthesis

Timeline ( Protein or DNA?)

1868- Meischer- DNA isolated from white blood cells

1900-Identification of the nucleic acids

1910-  Tetranucleotide hypothesis for DNA- Levene

1920- Purple dye found that stains DNA in the nucleus of cells

1920’s - Griffith experiments- smooth and rough pneumococcus in mice

1933- Chromosomal theory of genetics

1946- Muller- x-rays induces changes in chromosomes

1940’s Avery,McLeod , and McCarty- the transforming material is DNA

1940’s-   Luria and Delbruck- Bacteriophage studies

1940-1950- Linus Pauling studies proteins and identifies the alpha helix in proteins/  Biochemistry draws attention as a field of study.

1851- Isolation, purification, and analysis of DNA- Maurice Wilkins. Kings College. UK

1952- Martha Chase and Alfred Hershey- the blender experiment

1952- Erwin Chargaff-  A=T and C= G

1952- Rosalind Franklin- X-ray diffraction picture of DNA reveals the helix .Kings College. UK

1951-1953- The race for the double helix- James Watson and Francis Crick- Cambridge.UK

Exceptions to the Central Dogma( nuclear inheritance)

1. RNA viruses( + and – RNA)
2. Prions
3. Retroviruses ( reverse transcriptase )
4. Plasmids
5. Mitochondrial inheritance
6. Repetitive DNA
7. Structural DNA- telomeres and centromeres
8. Regulatory DNA
9. Intervening sequences in DNA
10. Retrotransposons
11. Transposons

DNA Facts

• Nucleotide building blocks
• Purines and pyrimidines.  Purine= adenine and guanine.    Pyrimidines = cytosine and thymine
• A= T and C=G.  Example.  23% of Adenine means that there is also 23% of T in the same type of DNA
• Deoxyribose( 5 Carbon sugar)
• Phosphates( negatively charge hydrophilic groups)
• Sugar-phsophate backbone on the outside of the DNA molecule
• Anti-parallel strands. 5’ – 3’ and 3’ to 5’. OH  hydroxyl group is on the 3’ and a phosphate group , PO4 is on the 5’ end of the sugar.  Anti-parallel established by the sugar, not the DNA
• Two long strands are coiled around a central axis
• The bases lie perpendicular to the axis, 3.4 Angstroms apart.
• Each complete turn of the helix is 34 Angstroms.  There are ten bases per turn
• The turns from major grooves and minor grooves
• The diameter of the molecule is 20 Angstroms ( 2 nm in diameter)
• Purines are opposite pyrimidines in the center of the molecule.  Three bases across on the inside.  Uniform space.

·         The bases are connected in the center of the molecule by hydrogen bonds

A       T                  C    G