Nucleic Acids
The Genetic Material
Two types of Nucleic acids
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RNA
DNA
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Stores hereditary
information
Made of monomers
called nucleotides
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DNA  Polymer : Nucleotide  Monomer
Each Nucleotide has 3 parts:
1) 5 carbon sugar  Deoxyribose
2) Phosphate group  PO4
3) Nitrogen Base
Identifying the Genetic Material

Experiments of Griffith and Avery yielded
results that suggested DNA was genetic
material (1944)

Hershey & Chase
used the
bacteriophage T2 and
radioactive labels to
show that virus genes
are made of DNA, not
protein (1952)
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DNA stores information that tells cells which
proteins to make and when to make them
The Structure of DNA

Discovered by
Watson & Crick in
1953 & received
Nobel Prize in 1962
along with Maurice
Wilkins
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DNA  Polymer : Nucleotide  Monomer
Each Nucleotide has 3 parts:
1) 5 carbon sugar  Deoxyribose
2) Phosphate group  PO4
3) Nitrogen Base
Nitrogen
Bases
Purines
Adenine
Guanine
Pyrimidines
Thymine
Cytosine
A
Human 30
Plant
27
Virus
21
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T
G
C
30
27
22
19
22
28
19
22
27
DNA forms a spiral
ladder  Double
Helix
Double helix is held
together by weak
Hydrogen bonds
Erwin Chargaff
Discovery
Chargaff’s Rule
A=T, G=C
DNA Replication
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Phase of Cell Cycle?
Why replicate?
Step 1: DNA Helicase
unzips DNA by breaking
weak Hydrogen bonds.
Step 2: DNA polymerase
adds nucleotides to
exposed nitrogen bases.
Step 3: Two DNA
molecules form that are
identical to original.
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DNA is referred to as “Semi-conservative”,
Each DNA molecule  1 template & 1 new
strand
DNA polymerase proofreads DNA during its
replication so that very few errors occur