MOLECULAR BIOLOGY OF THE GENE
I.Experiments showed that DNA is the genetic material
a.Knowledge of DNA is relatively new
b.DNA was known as a substance 100 years ago, but not known
as a hereditary agent until much later
c.GRIFFITH’S EXPERIMENT
i.Identified DNA as genetic carrier
ii.Involved a type of bacteria
iii.Harmless form was turned into harmful form when
placed with harmful form of bacteria
d.Chromosomes were known to be comprid of
i.Protein more versatile; 20 amino acids, therefore
thought to be genes
ii.DNA
e.HERSHEY and CHASE EXPERIMENT
i.Studied T2 bacteriophages (phages)
ii.Grew phages in radioactive elements
1.Sulfur for protein; phosphorous for DNA
iii.By tracing the radioactivity can determine what is the
hereditary carrier
iv.Results obtained, combined with earlier evidence
convinced scientific world that DNA was hereditary
material
II.DNA and RNA are polymers of nucleotides
a.NUCLEOTIDES → monomer of nucleic acid; phosphate group
+ sugar + nitrogenous ba
b.POLYNUCLEOTIDE → polymer of nucleotides
i.Becau the bas can appear in any quence, the
number of possible nucleotides is very large
c.SUGAR-PHOSPHATE BACKBONE → a repeating pattern of
sugar-phosphate-sugar-phosphate
d.DNA → Deoxyribonucleic Acid
i.Deoxyribo → deoxyribo; sugar found in the DNA
ii.Nucleic → found in the nucleus of the cell
iii.Acid → the phosphate group gives acidic properties
e. 4 types of bas found in DNA; 2 groups
i.PURINES (2 rings)
1.Adenine (A)
2.Guanine (G)
ii.PYRIMIDINES (1 ring)
1.Thymine (T)
2.Cytosine (C)
f.RNA → Ribonucleic Acid
i.Ribo → ribo; sugar found in RNA
1.Contains one more oxygen than deoxyribo
ii.Instead of T, RNA contains
1.URACIL (U)
III.DNA is a double stranded helix
a.Structure denotes function, so learning the shape of DNA was
crucial to understanding its role in hereditary
b.DOUBLE HELIX → two strands of DNA coiled around each
other explained by Watson and Crick
i.Ud data from Wilkins and Franklin
ii.Had X-Ray crystallography pictures of DNA
c.Watson and Crick explained double helix and that
i. A always joins with T
ii. C always join with G
iii.Allows from same distance between sugar backbones which matched data
IV.DNA replication depends on specific ba pairing
a.Watson and Crick’s model suggested a possible copying
mechanism
b.The specific pairing of complementary bas is how DNA is
logically copied
c.While the general mechanism of DNA replication is
conceptually simple, the actual process is quite complex V.DNA replication: A clor look
