1. DNA Replication

2. Before We Begin – Let’s Review  Take out your DNA Structure Worksheet Let’s grade it!!! Let’s grade it!!! 1. What is the full name of DNA? 2. What is a gene? 3. Where in the cell are chromosomes located? 4. What two scientists established the structure of DNA? 5. What is the shape of DNA?

3. 6. What are the sides of the DNA ladder made of? 7. What are the “rungs” of the ladder made of? 8. Adenine always binds with _______________________ and _____________________ always binds with Cytosine. 9. Using what you know about nitrogenous base pairing fill in the missing nucleotides: 10.Why is DNA called the “Blueprint of Life?”

4. A Perfect Copy  When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.

5. A Perfect Copy Cont. 1.On a sheet of scrap paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2.Hold the papers side by side, and compare the lines. Do they look the same? 3.Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4.How could you use the original paper to draw exact copies of the line without tracing it? 5.Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?

6. Duplicating DNA  During DNA replication: 1. The DNA molecule separates into two strands –Each strand of the double helix of DNA serves as a template, or model for the new strand 2. Two new complementary strands are produced following the rules of base pairing

7. The Semi-Conservative Replication Model Both strands of original DNA serve as templates Daughter chromosomes half old, half new DNA Replication

8. Replication Fork

9. How Replication Occurs 1.An enzyme called helicase unzips the DNA 2. An enzyme called DNA polymerase adds loose nucleotides to the growing strands

10. Picture It!!!

11. How Replication Occurs Cont. 3. An enzyme called ligase connects the Okasaki fragments together

12. Replication fork DNA polymerase New strand Original strand

13. How fast does in happen? IIIIn each of our cells, the DNA is being replicated at 50 – 500 nucleotides per second!!!

14. Let’s put you to the test! 1. The main enzyme involved in linking individual nucleotides into DNA molecules is a. Transfer RNA b. Ribose c. Helicase d. Polymerase

15. Let’s put you to the test! 2. The enzyme responsible for “gluing” the new strand of DNA together is: a. Polymerase b. Ligase c. Helicase d. Dunnocase

16. Let’s put you to the test! 3. During DNA replication, the DNA molecule separates into ____ strands. a. Four b. Three c. Two d. One

17. Let’s put you to the test! 4. T he sister chromosomes formed at the end of DNA replication consist of: a. H alf old, half new DNA b. A ll new DNA c. A ll old DNA

18. Let’s put you to the test! 5. DNA is replicated at a rate of 50 -500 nucleotides per: a. Day b. Hour c. Minute d. Second