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DNA

DNA. Structure and Function. The Role of DNA. Molecule of Heredity Stores information for various genetic traits Controls development and growth of each cell as well as the entire organism Copies itself : before a cell divides, genetic information must be copied

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DNA

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  1. DNA Structure and Function

  2. The Role of DNA • Molecule of Heredity • Stores information for various genetic traits • Controls development and growth of each cell as well as the entire organism • Copies itself : before a cell divides, genetic information must be copied • Transmits information from one generation to the next http://www.youtube.com/watch?v=l0TC9Lt7IGU&safe=active

  3. What is the structure of DNA and how was it discovered? • The Chemical Structure of DNA I: • http://www.youtube.com/watch?v=nExcd_wTcHg&safe=active

  4. Discovery of DNA Structure • Watson-Crick: worked together on DNA structure and came up with “double helix” model • Won Nobel Prize in 1962 • Helped by X-ray crystalography images by Rosalind Franklin • The Chemical Structure of DNA II: • http://www.youtube.com/watch?v=oZiAwqo77GM&safe=active

  5. Chargaff’s Ratios: • Helped scientist understand how the bases paired up • http://www.hhmi.org/biointeractive/media/DNAi_chargaff_ratio-lg.mov

  6. The Chemical Structure of DNA • DNA: (Deoxyribose Nucleic Acid) • Large Polymer Molecule • Two long chains of nucleotide subunits • Nucleotides from each chain pair up and bond together with hydrogen bonds Hydrogen bonds (weak) Strand 1 Strand 2

  7. Nucleotide Structure • 3 components of nucleotide: • 5 carbon deoxyribose sugar • Phosphate group • Nitrogenous Bases • Adenine, thymine, cytosine, guanine 4 bases possible (A, T, C, G) http://www.hhmi.org/biointeractive/media/DNAi_building_blocks-lg.mov

  8. Nitrogenous Base Pairs • Adenine - Thymine • Cytosine - Guanine

  9. Nucleotides join together into two long chains • Phosphate of one nucleotide is joined to sugar of next nucleotide by a covalent bond • The two chains are joined together by hydrogen bonds (weak bonds) between the nitrogenous bases. • Base pairs always A-T, C-G • http://www.youtube.com/watch?v=qy8dk5iS1f0&safe=active

  10. Double Helix Structure • Base pairs are rungs on a ladder • Sides of ladder are phosphate and sugar • Whole ladder is twisted into a “double helix” structure • Video: Chemical Structure of DNA III • http://www.youtube.com/watch?v=54n8DLreEe4&safe=active • http://www.hhmi.org/biointeractive/media/DNAi_paired_strands-lg.mov

  11. Nucleotide Base Sequence • Order of A, T, C, G nitrogenous bases eventually codes for different proteins. • The order of nucleotides is unique for different organisms • The more closely related two organisms are the more similar the DNA sequences • Way to determine evolutionary relationships

  12. Build a DNA Molecule • http://learn.genetics.utah.edu/content/begin/dna/builddna/

  13. DNA Replication • DNA duplicates itself prior to cell division • Each strand serves as a pattern or “template” to make a new DNA molecule

  14. Enzymes: • Break open (unzip) weak H-bonds between bases pairs • Bind free nucleotides to complimentary bases of unzipped single strand • (DNA polymerase)

  15. Produces 2 identical DNA double helix strands (called complimentary strands) • Each new strand made of one of the original strands plus one new synthesized strand. • http://www.youtube.com/watch?v=z685FFqmrpo&safe=active • http://www.youtube.com/watch?v=zdDkiRw1PdU&safe=active

  16. Focus Question • Why is accuracy so important in replication of DNA?

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