Objectives – Chromosome Structure 1. Describe the main functions of DNA packaging. 2. What is a chromosome? 3. Define genome. 4. What are the main causes for decrease in gene density as the apparent complexity of the organism increases? 5. What are intergenic sequences? What are the two main types of intergenic sequences? 6. Define chromatin. 7. What are the structural components of a nucleosome? a) Be able to draw schematically the structure of the histones and DNA in a nucleosome. Know the five types of histones (which are part of the “core”?) 8. How does the DNA interact with the histones in a nucleosome? 9. Describe and explain the micrococcal nuclease experiment. a) You should understand the foundations of this experiment and be able to interpret and draw conclusions from alternative results. 10. Describe the three types of post-translational modifications that can be made to histones. What is the functional significance of each modification? 11. What is the 30 nm fiber structure of chromatin? Explain the difference between the solenoid model and the zigzag model. What is the function of Histone H1 in the 30 nm fiber structure? 12. Explain the “popular” model for the next level of chromosome organization (it is known as the 300-nm fiber). How is the nuclear scaffold thought to be involved in this level of organization? 13. Compare and contrast euchromatin and heterochromatin.