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Section12.2. 1. Structure of DNA. Components of DNA. DNA (deoxyribonucleic acid) is a nucleic acid made up of nucleotides joined into long strands by covalent bonds. Nucleotides. Nucleotides are building blocks of nucleic acids Nucleotides: 3 parts 5-carbon sugar: deoxyribose
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Section12.2 1. Structure of DNA
Components of DNA • DNA (deoxyribonucleic acid) is a nucleic acid made up of nucleotides joined into long strands by covalent bonds
Nucleotides • Nucleotides are building blocks of nucleic acids • Nucleotides: 3 parts • 5-carbon sugar: deoxyribose • Phosphate group • Nitrogenous base • 4 Nitrogenous bases (contain Nitrogen): • Adenine • Guanine • Thymine • Cytosine
Bonds • Nucleotides joined by covalent bonds • Forms between sugar of one nucleotide and phosphate group of the next. Nitrogenous bases -Stick out sideways from the nucleotide chain -Nucleotides can be joined together in a number of different ways -Any base sequence is possible -That’s what makes us so different! -Have a special chemical structure that is especially good at absorbing UV light
Stop and Write(2-5 min.) • 1. What are the 3 components of a nucleotide? • 2. What are the four nitrogenous bases? • 3. Do you think excessive UV light could damage your DNA? How?
Erwin Chargaff • Austrian-American biochemist • Discovered that % of: • Adenine [A]= Thymine [T] • Guanine[G]= Cytosine [C] P. 345 Analyzing data #1-4 (5 min.)
2. Double- helix • Explains Chargaff’s rule • Antiparallel strands • DNA runs in opposite directions Hydrogen bonds -Both strands of DNA are held together by H bonds between nitrogenous bases (A and T) and (G and C). -Base pairing -A always lines up perfectly with T -G always lines up perfectly with C
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