DNA: The Genetic Material. The Structure of DNA The Replication of DNA.
It’s the DNA!
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Transcript of It’s the DNA!
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It’s the DNA!
The information is in the DNA!
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DNA History
• Griffith (1928)– Experimented on mice and observed some harmless strains of bacteria could change into harmful strains. He called this transformation.
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DNA History
• Avery (1944) – Discovered that DNA is the nucleic acid that stores and transmits the genetic information from one generation to the next.
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The Avery Experiment (1944)
Purified DNA extracted from the smooth pneumonia bacteria could ‘transform’ rough pneumonia bacteria into the smooth form.
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The Hershey-Chase experiment (1952)
Viruses called bacteriophages can infect bacterial cells and change the characteristics of the cells.Bacteriophages are only made of two materials… protein and DNA.
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DNA Nucleotide
OO=P-O O
Phosphate Group
CH2
O
C1C4
C3 C2
5
Sugar(deoxyribose)
N
Nitrogenous base (A, G, C, or T)
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DNA’s StructureDNA contains four nucleotide bases: –adenine (A) –cytosine (C) –guanine (G)–thymine (T)
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Nitrogenous Bases
PURINES1. Adenine (A)
2. Guanine (G)
PYRIMIDINES3. Thymine (T)
4. Cytosine (C) T or C
A or G
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Chargaff’s Rules (1950)• Chargaff discovered
how the nitrogenous bases bond together.
• He discovered that the amount of Adenine equals the amount of Thymine ,and that the amount of Cytosine equals the amount of Guanine.
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Chargaff’s Rule
Adenine pairs with Thymine
Guanine pairs with Cytosine
Their amounts in a given DNA molecule will be about the same.
G CT A
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P
P
P
O
O
O
1
23
4
5
5
3
3
5
P
P
PO
O
O
1
2 3
4
5
5
3
5
3
G C
T A
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More DNA History
• Watson & Crick created the double helix model of DNA.
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DNA Double Helix
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How does all this DNA fit into a cell?
• In Eukaryotes, DNA is located in the nucleus in the form of chromosomes.
• Chromosomes are DNA wound tightly around proteins called histones.
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Semi-Conservative Replication
One-half of each new molecule of DNA is old (template strand)One-half of new molecule of DNA is new (complementary strand)
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DNA Replication
• During DNA replication, the DNA molecule separates into two strands, then produces two new complimentary strands following the rules of base pairing
(Chargaff Rules).
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DNA Replication
• Each strand of DNA serves as a template, or model, for the new strand.
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How It Occurs
• Complimentary bases are added to the strands, for example a strand of DNA with the bases
ATTCGAG would have a complimentary strand of
• TAAGCTC
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How It Occurs
•DNA replication is carried out by a series of enzymes.