1. Objectives Outline the structure of DNA including DNA nucleotides, base pairing and explain how the structure forms. Outcomes (3) Describe the components of DNA. (5) Explain the overall structure of DNA. (7) Explain how the different components of DNA arranged and link together. Key terms: deoxyribose, sugar, base, nucleotide.

2. Read the journal article by Watson & Crick and then answer the following questions: 1.What was the ‘new’ structure of DNA proposed by Watson & Crick described as? 2.What is the type of bond between the bases called? 3.For bonding to occur a purine must join to what? 4.What are the two purine bases called? 5.What are the other two bases called? Outcomes (3) Describe the components of DNA. (5) Explain the overall structure of DNA. (7) Explain how the different components of DNA arranged and link together. Key terms: deoxyribose, sugar, base, nucleotide.

3. Introduction to nucleotides Nucleotides are nitrogen-containing organic substances that form the basis of the nucleic acids DNA and RNA. All nucleotides contain the following three groups: In DNA the sugar is deoxyribose, whereas in RNA the sugar is ribose. a phosphate group a pentose sugar a nitrogen-containing base

4. Bases There are five bases, split into two types: adenine (A) and guanine (G) are purine bases. AG TU thymine (T), cytosine (C) and uracil (U) are pyrimidine bases. DNA contains A, G, T and C, whereas RNA contains A, G, U and C. C

6. Base pairing rules

7. Use the sweets and cocktail sticks to model the structure of DNA. Use the rules on the board. What are the limitations of the model? What are the strengths? How could you improve the model? Use what we have done to draw the structure of a nucleotide and how they join together. Outcomes (3) Describe the components of DNA. (5) Explain the overall structure of DNA. (7) Explain how the different components of DNA arranged and link together. Key terms: deoxyribose, sugar, base, nucleotide.

12. Structure of DNA

13. Outcomes (3) Describe the components of DNA. (5) Explain the overall structure of DNA. (7) Explain how the different components of DNA arranged and link together. Key terms: deoxyribose, sugar, base, nucleotide.