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DNA - PowerPoint PPT Presentation

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DNA
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  1. DNA Structure and Function

  2. WHAT IS DNA? • DNA stands for DeoxyriboNucleic Acid • The main job of DNA is to make PROTEINS

  3. Function of DNA • DNA contains genes that codes for all of our traits • It is your genetic material or “program” or “blueprint” • DNA is what makes youfunction and be who you are today • Passed from cell to cell

  4. Location of DNA • DNA is found in the nucleusof the cellfor eukaryotes • DNA is found in the cytoplasm for prokaryotes (ex: bacteria) • Our genes are on our chromosomes. • Chromosomes are made up of a chemical called DNA

  5. Building Blocks of DNA • Each nucleotide consists of • Deoxyribose (5-carbon sugar) • Phosphate group • A nitrogen-containing base (A, G, T, C)

  6. Phosphate Group O=P-O O CH2 O N Nitrogenous base (A, G, C, or T) C C Sugar (deoxyribose) C C Nucleotide Structure

  7. A or G T or C Nitrogen Bases • Adenine (A) • Guanine (G) • Thymine (T) • Cytosine (C)

  8. Structure of DNA • Double Helix: Watson-Crick Model • Strands are held together by hydrogen bondsbetween bases • The sides are a sugar-phosphate backbone, while the “rungs” of the ladder are the bases. • The DNA strands run in opposite directions

  9. Base-Pairing Rules • Adenine (A) pairs with Thymine (T) • Cytosine (C) pairs with Guanine (G)

  10. There are two classes of nitrogen bases called purines (double-ringed structures) and pyrimidines (single-ringed structures). The four bases in DNA's alphabet are: • adenine (A) - a purine • cytosine(C) - a pyrimidine • guanine (G) - a purine • thymine (T) - a pyrimidine

  11. DNA COPY PRACTICE • Make a copy of the following DNA Sequence: • DNA (Original): C G G T A • COPY: G C C A T • DNA(Original): A T C G C G A A • COPY: T A G C G C T T

  12. Chargaff’s Rule • A = T C = G • A+T+C+G = 100 • For example: The DNA is made up of 15% Adenine. Figure out the amount of the other nitrogen bases. • Adenine = Thymine Thymine = 15 • (a)G+C+15+15=100 (b)100-15-15=G+C (c)100-30 = 70 • G+C = 70 and Guanine =Cytosine • G= 35 and C=35 • Therefore: A=15%, T=15%, G=35%, C=35%

  13. Practice Problem • The DNA is made up of 30% Cytosine, figure out the amount of the other nitrogen bases. • Cytosine = Guanine G=30 • 30+30+A+T=100 • A+T= 100-30-30 • T+A=40 • A=20, T=20 • Therefore: G=30, C=30, A=20, T=20