3000 BC
Evidence of selective breeding in
crops and animals from ancient
Chinese and Sumerian farmers
1866
Gregor Mendel publishes his work
on peas and heredity
1869
Friedrich Miescher discovers the
acidic substance in the nucleus of
all cells; calls it “nuclein”
NUCLEIC ACID
1928
Frederick Griffith fails at making a vaccine for
pneumonia; discovers “Transformation Principle”
1928
Frederick Griffith fails at making a vaccine for
pneumonia
1929
Phoebus Levene discovers structures present in
DNA: deoxyribose sugar, phosphate groups, and
one of four bases (A,T,G,C)
1928
Frederick Griffith fails at making a vaccine for
pneumonia
1929
Phoebus Levene discovers structures present in
DNA: deoxyribose sugar, phosphate groups, and
one of four bases (A,T,G,C)
1944
Oswald Avery, Colin MacLeod, and Maclyn
McCarty show that DNA, and not protein, is the
"transforming factor" Griffith first identified.
1950
Erwin Chargaff discovers ratio of bases;
A=T, G=C “Chargaff’s Rule”
1950
Erwin Chargaff discovers ratio of
bases;
A=T, G=C “Chargaff’s Rule”
1952
Maurice Wilkins and Rosalind
Franklin take
X-ray images of DNA crystals used
by Watson and Crick
1953
James Watson and Francis Crick
discover the structure of DNA
1985
PCR developed
1989 First exoneration using DNA
1996
Dolly, the sheep; first
mammal to be cloned
2003
Human Genome is sequenced
NUCLEOTIDE
Bases
Adenine = Thymine
Cytosine = Guanine
held together by hydrogen
bonds
Backbone
Sugar phosphate
~10 base pairs per 360° turn
DNA is normally in chromatin state