DNA
2
DNA Functions
• Stores genetic information to build and maintain a living organism
• Copies itself
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James Watson & Francis Creek 1953
• Determined the three-dimensional structure of DNA
• One of the greatest discoveries in the history of science
• Nobel prize in 1962
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• Made of repeating units called nucleotides
• Each nucleotide made of a sugar named deoxyribose, a phosphate and a base
5
DNA Nucleotide
Deoxyribose
Phosphate
Base =
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Nucleotides Form a Double Strand
Deoxyribose
Phosphate
Base
7
DNA Molecule is Double Stranded
8
Base Pairing Rule
• Adenine pairs with Thymine
• Guanine pairs with Cytosine
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DNA• Total length of DNA in each
cell is about 6 feet
• Wraps around proteins called histones
• Over 3 billion nucleotide pairs in human DNA!
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DNA ReplicationDNA strands separate
DNA nucleotides attach to
each strand
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Each new DNA
molecule will
be an exact copy of the
original
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First, DNA strands separate
13
Second, an RNA attaches to DNA strand
DNA cannot start replication on its own
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Third, DNA nucleotides are attached to DNA
strand
15
Fourth and final, the RNA is removed
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DNA Errors• Replication is not 100% accurate
–Errors occur when copying DNA• DNA damaged
–Ultraviolet light–X-rays–Cigarette smoke–Nitrates (smoked meat)–Pesticides & Herbicides
17 The End