1. DNA Structure and Replication of DNA

2. Chromosomes

3. DNA Replication Makes sure that each daughter cell will have the genetic information it needs to carry out its activities. Page 101

4. Structure of DNA -Twisted ladder or spiral staircase -Sides of the ladder are made up of molecules of a sugar called deoxyribose -Sides of the ladder alternate with phosophate molecules

5. Rungs of DNA Ladder -Each rung is made up of a pair of molecules called nitrogen bases DNA has four kinds of nitrogen bases: -adenine (A) -thymine (T) -guanine (G) -cytosine (C)

6. Nitrogen Bases Bases on one side of the ladder pair with the bases on the other side. -Adenine pairs only with thymine A pairs with T -Guanine pairs only with cytosine G pairs with C Page 101

7. REVIEW!!!! 1. What is the shape of DNA? 2. What are the sides of DNA made of? 3. What are the rungs of the ladder made of? 1.Double Helix 1.Sugars and phosphates 1.Nitrogen bases

8. 4.What does the letter C represent? 4.What does the letter A represent? 4.What does the letter T represent? 4.What does the letter G represent? 4.Cytosine 4.Adenine 6. Thymine 7. Guanine

9. 8.How many chromosomes are in the body cells of the human body? 9. How many chromosomes in human sex cells? 8. 46 9. 23