1. DNA: Replication and Chromosomes Paraphrase Notes (Presentation is on my website)

2. DNA Organization How do cells organize their DNA inside the nucleus? Discuss and be ready to share. Either: 1) Spread out. Why? So DNA can be read to make proteins 2) Packed very closely together. Why? So DNA can be moved around the cell (in mitosis) Packed together often DNA referred to as “chromosomes”

3. Chromosomes DNA tightly wrapped around histones (a type of protein) Nucleosomes = bundles of histones Chromosomes = LOTS of tightly-packed nucleosomes Diagram in textbook (297) Explain the “yarn/paper towel holder” analogy in your notebook

4. Replication Why would cells ever need to replicate (copy) their DNA? Discuss, be ready to share. Cells replicated (copy) their DNA for mitosis To make more cells! HOW would a cell copy its DNA? Discuss, be ready to share? Hint: are hydrogen bonds easy to break or hard to break? DNA opens up into two separate strands New bases are added!

5. Replication – the details Helicase unzips DNA DNA polymerase Adds new bases Spell checks Demonstration on the board! http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna -rna2.swf http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna -rna2.swf