1. End Show 12–2 Chromosomes and DNA Replication Slide 1 of 21 Copyright Pearson Prentice Hall Pages 295 - 299 DNA REPLICATION

2. End Show 12–2 Chromosomes and DNA Replication Slide 2 of 21 ProkaryotesEukaryotes nucleus Chromosome shape # of chromosomes Location of chromosome(s)

3. End Show 12–2 Chromosomes and DNA Replication Slide 3 of 21 Copyright Pearson Prentice Hall DNA and Chromosomes Chromosome E. Coli Bacterium Bases on the Chromosomes

4. End Show 12–2 Chromosomes and DNA Replication Slide 4 of 21 Copyright Pearson Prentice Hall Prokaryotes- single chromosome circular no nucleus cytoplasm Eukaryotes- # of chromosomes vary for different species in nucleus more DNA than prokaryotes double helix ( twisted ladder), coiled to fit

5. End Show 12–2 Chromosomes and DNA Replication Slide 5 of 21 DNA and Chromosomes Chromosome Structure DNA and protein, tightly packed together to form chromatin. Chromatin consists of DNA tightly coiled around proteins called histones. DNA and histone molecules form nucleosomes. Nucleosomes pack together, forming a thick fiber. Copyright Pearson Prentice Hall

6. End Show 12–2 Chromosomes and DNA Replication Slide 6 of 21 Copyright Pearson Prentice Hall DNA and Chromosomes Eukaryotic Chromosome Structure Chromosome Supercoils Nucleosome DNA double helix Histones Coils

7. End Show 12–2 Chromosomes and DNA Replication Slide 7 of 21 DNA Replication before a cell divides- which phase of the life cycle of the cell? In most prokaryotes, DNA replication begins at a single point and continues in two directions. Copyright Pearson Prentice Hall

8. End Show 12–2 Chromosomes and DNA Replication Slide 8 of 21 Copyright Pearson Prentice Hall DNA Replication Eukaryotes- DNA replication occurs at hundreds of places and in both directions Replication forks = the place where separation and replication is occuring

9. End Show 12–2 Chromosomes and DNA Replication Slide 9 of 21 Copyright Pearson Prentice Hall DNA Replication During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.

10. End Show 12–2 Chromosomes and DNA Replication Slide 10 of 21 Copyright Pearson Prentice Hall DNA Replication Nitrogen Bases Replication Fork DNA Polymerase Replication Fork Original strand New Strand Growth

11. End Show 12–2 Chromosomes and DNA Replication Slide 11 of 21 Steps for Replication 2 strands of DNA unwind and separate Why is this easy to do? What breaks? Helicase = enzyme that breaks this _____ Copyright Pearson Prentice Hall

12. End Show 12–2 Chromosomes and DNA Replication Slide 12 of 21 DNA Polymerase Enzyme Causes new nucleotides to attach to the old strand Proof reads to ensure correct sequence Covalent bonds (harder to break )link the outside of the ladder together- sugar & phosphate H-bonds connect the 2 nucleotides together at the nitrogen bases – easier to break Copyright Pearson Prentice Hall

13. End Show 12–2 Chromosomes and DNA Replication Slide 13 of 21 Mutations Occur if sequence of the nucleotides change Frequency of occurrence is 1/1billion Enzymes check for accuracy and will repair errors Copyright Pearson Prentice Hall

14. End Show Slide 14 of 21 Copyright Pearson Prentice Hall 12–2 In prokaryotic cells, DNA is found in the a.cytoplasm. b.nucleus. c.ribosome. d.cell membrane.

15. End Show Slide 15 of 21 Copyright Pearson Prentice Hall 12–2 The first step in DNA replication is a.producing two new strands. b.separating the strands. c.producing DNA polymerase. d.correctly pairing bases.

16. End Show Slide 16 of 21 Copyright Pearson Prentice Hall 12–2 A DNA molecule separates, and the sequence GCGAATTCG occurs in one strand. What is the base sequence on the other strand? a.GCGAATTCG b.CGCTTAAGC c.TATCCGGAT d.GATGGCCAG

17. End Show Slide 17 of 21 Copyright Pearson Prentice Hall 12–2 In addition to carrying out the replication of DNA, the enzyme DNA polymerase also functions to a.unzip the DNA molecule. b.regulate the time copying occurs in the cell cycle. c.“proofread” the new copies to minimize the number of mistakes. d.wrap the new strands onto histone proteins.

18. End Show Slide 18 of 21 Copyright Pearson Prentice Hall 12–2 The structure that may play a role in regulating how genes are “read” to make a protein is the a.coil. b.histone. c.nucleosome. d.chromatin.