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DNA Structure and Replication
Cell Nucleus Chromosomes DNA Biology 1-2
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Essential Questions/Objectives
What is DNA? How does it copy itself before cells divide? Explain the structure of DNA.
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James Watson and Francis Crick:
Discovered the structure of DNA in 1953. Discussed probable mode of replication.
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DNA Replication
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Complementary Strands Separate
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Parent Strands Serve as Template
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Nucleotides connected
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Phosphate, Sugar and a Base Cytosine Without Guanine
DNA Song We Love DNA Made of Nucleotides Phosphate, Sugar and a Base Bonded Down One Side Adenine and Thymine Make a Lovely Pair Cytosine Without Guanine Would Feel Very Bare
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What’s a Nucleotide? Phosphate Base Sugar
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DNA includes 4 nitrogenous bases:
Adenine pairs with Thymine Guanine pairs with Cytosine
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DNA is double stranded:
Hydrogen bond connects the base pairs. Double Helix
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D = Deoxyribose Pentose Sugar: 5 sides
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Deoxyribose Nucleic Acid (DNA)
Phosphate Group Adenine P A Thymine P T Nitrogenous Base Nucleotide deoxyribose P Pentose Sugar Phosphodiester Bond Hydrogen Bonds P Cytosine Guanine C G
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DNA Model P G A T P S A S P S C P S T P
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DNA Components Backbone components: Sugar (deoxyribose)
Phosphate group Bases: Adenine, Thymine, Cytosine, Guanine Base Pairs: Adenine and Thymine always pair up with 2 hydrogen bonds. Cytosine and Guanine always pair up with 3 hydrogen bonds.
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DNA Structure Quiz Use the key on the right to construct a model of DNA showing 4 base pair matches. On the finished model circle and label one nucleotide and show where hydrogen bonds are located. Also, in writing or with a drawing show how your model of DNA would replicate and what the finished product of one replication would be. = phosphate = adenine = cytosine = guanine = thymine = sugar (deoxyribose)
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