DNA: The Genetic Material

DNA
Deoxyribonucleic Acid

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DNA  Polymer : Nucleotide  Monomer
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Each Nucleotide has 3 parts:
1) 5 carbon sugar  Deoxyribose
2) Phosphate group  PO
4
3) Nitrogen Base

Nitrogen
Bases
Adenine
Purines
Guanine
Pyrimidines
Thymine Cytosine

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Identifying the Genetic Material
Experiments of Griffith and Avery yielded results that suggested DNA was genetic material (1944)

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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

A
Human 30
Plant 27
Virus 21
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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
T
30
27
22
G
19
22
28
C
19
22
27

Rosalin Franklin

The Structure of DNA
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Discovered by
Watson & Crick in
1953 received Nobel Prize in 1962 along with
Maurice Wilkins

DNA Replication
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Phase of Cell Cycle?
Why replicate?
Step 1: DNA Helicase unzips DNA by breaking weak Hydrogen bonds.
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Step 2: DNA polymerase adds nucleotides to exposed nitrogen bases.
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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

The secrets of the sequence http://www.youtube.com/watch
?v=sf0YXnAFBs8