bag DNA Subunit Models. Store the remaining parts for use in Activity 12, “ DNA Replication.” teaching suMMaRy Getting Started • Students discuss their ideas about the structure of dnA. Doing the Activity • Students build a dnA model. Follow-up • Students analyze the strengths of various dnA models. modeling • 2 class sessions ...

Before a cell can reproduce, it must first replicate, or make a copy of, its DNA. Where DNA replication occurs depends upon whether the cells is a prokaryote or a eukaryote (see the RNA sidebar on the previous page for more about the types of cells). DNA replication occurs in the cytoplasm of prokaryotes and in the nucleus of eukaryotes. called DNA replication. In DNA replication, the double helix ladder is untwisted and the two strands are separated by breaking the hydrogen bonds between the base pairs. 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 fi lls