Worksheet 10: The Structure of DNA Biology Directions: Answer in complete sentences. 1. What are nucleotides? 2. What are the three parts of each nucleotide? 3. What are the four different types of DNA nucleotides? 4. Which part of the nucleotides is the same and which part is different? 5. What bases have single ring structure? 6. What bases have double ring structure? 7. Is the DNA made of equal amounts of nucleotides in all organisms? 8. What is a double helix? 9. How are the two sides of the double helix held to each other? 10. How many hydrogen bonds does A and T form? What about C and G?