Do Now: Do Now: Take out homework. Then… 1. What is the monomer of nucleic acids? 2. What are the 3 parts a DNA strand? 3. What are the 4 different nitrogenous bases and how do they pair? Homework:

How to make a copy of DNA

DNA Replication occurs inside the nucleus right before cell division. Because… Enzymes and free- nucleotides are available DNA would become destroyed in the cytoplasm

DNA Replication is necessary for making more cells. It must occur before Mitosis and Meiosis.

DNA Replication occurs during the S-phase of the Cell Cycle

Step 1: Helicase Breaks hydrogen bonds It unwinds and separates the double helix Creates several replication forks in the DNA strand.

This occurs at multiple Origins of Replication, and creates replication bubbles

Step 2: DNA Polymerase reads the DNA template and attaches complementary nucleotides It also proofreads and makes corrections

DNA Polymerase only attaches new nucleotides to the 3’ end of the new strand It’s like reading a book straight through (leading strand) Or reading a book by chapter beginning with the last chapter (lagging strand).

Step 3: DNA ligase fuses the gaps in the new sugar-phosphate backbone utube.com/w atch?v=teV62 zrm2P0

Results: Finally, there are two identical “daughter DNA” molecules WATCH IT HAPPEN!!! WATCH IT HAPPEN!!!

***You are left with 2 exactly identical strands of DNA double helix.*** Original strands of DNA Original OONN New

DNA Replication is semi-conservative Each new molecule of DNA has one of the original strands and one newly copied strand.

Answer the following Questions: 1.Where in the cell does DNA replication occur? 2.List the 3 enzymes involved and their functions. 3.What should be the result of DNA Replication? 4.Explain why DNA Replication is called a semi- conservative process.

A T G C C G T A A T G C ATGCCGCGTATGCCGCGT TACGGCGCATACGGCGCA 5’ 3’ 1.Label the 5’ and 3’ ends of the complementary strand. 2.Imagine you are DNA polymerase and fill in the complementary nucleotides for the portions of DNA that are ready to be replicated. 3.Which strand will be the leading strand? How can you tell? 4.Identify the Old DNA and the New DNA segments.

Build a model of DNA 9 base pairs Blue tubes = cytosine Yellow tubes = guanine Green tubes = thymine Orange tubes = adenine White tubes = phosphates White rods = hydrogen bonds Black pentagons = deoxyribose (sugar)