Notes on DNA and DNA structure


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Notes on DNA and DNA structure

  1. 1. DNA STRUCTURE<br />
  2. 2.<br />History of DNA<br />
  3. 3.<br />Deoxyribonucleic Acid<br />DNA  is a complex molecule found in all living things.<br />The primary function of DNA is tostore and transmit genetic information  that tells cells which proteins to make and when to make them. <br />
  4. 4. In 1953, James Watson and Francis Crick proposed a model for the DNA molecule that consisted of two nucleotide chains that wrap around each other to form a double spiral. This shape is called a double helix. <br />
  5. 5. An idea about size:<br /> An average cell nucleus is about 6 micrometers in diameter.<br />  The total length of the DNA in the human genome is 1.8 meters.<br />  There must be several levels of coiling and supercoiling in DNA. <br />
  6. 6. Chromosome:         a coiled, double rod-shaped form of condensed DNA that forms during cell division.<br />
  7. 7. DNA BASE PAIRS<br />
  8. 8. Using Models<br />What is a model?<br />Why is modeling important to scientists?<br />What are the advantages and/or disadvantages of using models? <br />
  9. 9. Build a Model of DNA using candy:<br />
  10. 10. KEY:<br />Sugar – Twizzler (5 per side)<br />Phosphate- Marshmallow (5 per side)<br />Bases: <br /> Adenine (A) – orange jelly<br /> Thymine (T) – mango jelly<br /> Cytosine (C) – grape jelly<br /> Guanine (G) - strawberry jelly <br />Task 1: Build a Model of DNA using candy.<br />Note: Use string as backbone of ladder<br />Task 2: Label the plate of your candy DNA .<br />
  11. 11. Guide questions: Write your answers in <br />your notebook.<br />Draw and label your DNA candy model.<br />What molecules make up the sides of the ladder? <br />a. What molecules make up the rung (at the middle) of the ladder? b. How do the molecules in the rungs pair up? c. What side molecule are they attached to?<br />What is the sequence (code) of your DNA model? <br />
  12. 12. DNA MODEL<br />A molecule of DNA (Deoxyribonucleic Acid) is composed of two backbones and four types of chemical bases. <br />Side of the Ladder: <br /><ul><li>A chain of phosphate groups and sugars forms the sides of the ladder.
  13. 13. Each sugar molecule in the ladder provides an</li></ul>attachment site for one of the chemical bases.<br />Steps of the ladder: <br />The four types of chemical bases are: adenine, thymine, cytosine and guanine. They usually are represented by their first letters: A, T, C and G.<br />
  14. 14. The bases form pairs in a very specific way: <br />A pairs with T, <br />C pairs with G.<br />
  15. 15. <ul><li>The DNA sequence is the consecutive order of bases on one side, or strand, of the </li></ul>twisted ladder. <br /><ul><li>The other strand has a complementary sequence determined by the base</li></ul>pairing rules.<br />
  16. 16. DNA Model Kit<br />Steps:<br />Construct support stand. Attach 3 legs to black 4-prong center and attach long green straw.<br />Construct 12 sets of sugar + base combination. <br /> Attach a base (A,T, C, G) to a black 3-prong center. <br />Construct 6 pairs of sugar + base combination. Insert 6 white 2-prong centerpiece to the long green straw. Connect each sugar and N-base combination to the white center. Note base pairings (A-T, C-G).<br />Construct phosphate group. Attach 2 yellow connectors to each end of red 2-prong center to make 6 sets. Connect the phosphates to each end of the sugars (black center). <br />End the chain. Attach a red center to the end of the sugars (end). <br />Make a double helix. Twist the chain by turning each white center and sliding it along the long green straw. <br />Legend: <br />Support: <br />1 Long Green Straw Support stand<br />3 2” straw Support stand<br />1 black 4-prong center Support stand<br />Bonds (Connectors):<br />White 2-prong center (Sugar to base <br />and Sugar to Phosphate connector)<br />Yellow (Sugar to phosphate connector)<br />Nitrogen bases:<br />Blue straw Adenine (A)<br />Red straw Thymine (T)<br />Grey Cytosine (C)<br />Green Guanine (G) <br />Sugars: <br />Black 3-prong center<br />Phosphate Group:<br />Red 2-prong center<br />Base Pairs: <br />A----T<br />C----G<br />
  17. 17. ADDITIONAL NOTES: <br />The specific matching of the base pairs, A with T and C with G, provides a way for exact copies of DNA to be made.<br />To make exact copies of DNA, the double helix ladder is untwisted and separates the two strands. <br />Next, two new strands are made by reading each side of the DNA ladder, one step (base) at a time. At each step, the matching base fills in (with its associated sugar and phosphate) to complete the rung and lengthen the new DNA strand.<br />When the process is complete, there are two identical DNA double helices, each containing one original and one new strand.<br />Copying of DNA is an important part in making new cells. Before a cell divides, it first duplicates its DNA so that the new cell will have the same genetic information. <br />The specific base pair matching during replication ensures that exact DNA copies are made.<br />